User space can use the MEM_OP ioctl to make storage key checked reads
and writes to the guest, however, it has no way of performing atomic,
key checked, accesses to the guest.
Extend the MEM_OP ioctl in order to allow for this, by adding a cmpxchg
op. For now, support this op for absolute accesses only.
This op can be use, for example, to set the device-state-change
indicator and the adapter-local-summary indicator atomically.
Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
---
include/uapi/linux/kvm.h | 8 +++
arch/s390/kvm/gaccess.h | 3 ++
arch/s390/kvm/gaccess.c | 103 +++++++++++++++++++++++++++++++++++++++
arch/s390/kvm/kvm-s390.c | 56 ++++++++++++++++++++-
4 files changed, 169 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 55155e262646..d2f30463c133 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -583,6 +583,8 @@ struct kvm_s390_mem_op {
struct {
__u8 ar; /* the access register number */
__u8 key; /* access key, ignored if flag unset */
+ __u8 pad1[6]; /* ignored */
+ __u64 old_addr; /* ignored if cmpxchg flag unset */
};
__u32 sida_offset; /* offset into the sida */
__u8 reserved[32]; /* ignored */
@@ -595,11 +597,17 @@ struct kvm_s390_mem_op {
#define KVM_S390_MEMOP_SIDA_WRITE 3
#define KVM_S390_MEMOP_ABSOLUTE_READ 4
#define KVM_S390_MEMOP_ABSOLUTE_WRITE 5
+#define KVM_S390_MEMOP_ABSOLUTE_CMPXCHG 6
+
/* flags for kvm_s390_mem_op->flags */
#define KVM_S390_MEMOP_F_CHECK_ONLY (1ULL << 0)
#define KVM_S390_MEMOP_F_INJECT_EXCEPTION (1ULL << 1)
#define KVM_S390_MEMOP_F_SKEY_PROTECTION (1ULL << 2)
+/* flags specifying extension support via KVM_CAP_S390_MEM_OP_EXTENSION */
+#define KVM_S390_MEMOP_EXTENSION_CAP_BASE (1 << 0)
+#define KVM_S390_MEMOP_EXTENSION_CAP_CMPXCHG (1 << 1)
+
/* for KVM_INTERRUPT */
struct kvm_interrupt {
/* in */
diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h
index 9408d6cc8e2c..b320d12aa049 100644
--- a/arch/s390/kvm/gaccess.h
+++ b/arch/s390/kvm/gaccess.h
@@ -206,6 +206,9 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
void *data, unsigned long len, enum gacc_mode mode);
+int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len, __uint128_t *old,
+ __uint128_t new, u8 access_key, bool *success);
+
/**
* write_guest_with_key - copy data from kernel space to guest space
* @vcpu: virtual cpu
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 0243b6e38d36..74cb728a0f24 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -1161,6 +1161,109 @@ int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
return rc;
}
+/**
+ * cmpxchg_guest_abs_with_key() - Perform cmpxchg on guest absolute address.
+ * @kvm: Virtual machine instance.
+ * @gpa: Absolute guest address of the location to be changed.
+ * @len: Operand length of the cmpxchg, required: 1 <= len <= 16. Providing a
+ * non power of two will result in failure.
+ * @old_addr: Pointer to old value. If the location at @gpa contains this value,
+ * the exchange will succeed. After calling cmpxchg_guest_abs_with_key()
+ * *@old_addr contains the value at @gpa before the attempt to
+ * exchange the value.
+ * @new: The value to place at @gpa.
+ * @access_key: The access key to use for the guest access.
+ * @success: output value indicating if an exchange occurred.
+ *
+ * Atomically exchange the value at @gpa by @new, if it contains *@old.
+ * Honors storage keys.
+ *
+ * Return: * 0: successful exchange
+ * * a program interruption code indicating the reason cmpxchg could
+ * not be attempted
+ * * -EINVAL: address misaligned or len not power of two
+ * * -EAGAIN: transient failure (len 1 or 2)
+ * * -EOPNOTSUPP: read-only memslot (should never occur)
+ */
+int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
+ __uint128_t *old_addr, __uint128_t new,
+ u8 access_key, bool *success)
+{
+ gfn_t gfn = gpa >> PAGE_SHIFT;
+ struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
+ bool writable;
+ hva_t hva;
+ int ret;
+
+ if (!IS_ALIGNED(gpa, len))
+ return -EINVAL;
+
+ hva = gfn_to_hva_memslot_prot(slot, gfn, &writable);
+ if (kvm_is_error_hva(hva))
+ return PGM_ADDRESSING;
+ /*
+ * Check if it's a read-only memslot, even though that cannot occur
+ * since those are unsupported.
+ * Don't try to actually handle that case.
+ */
+ if (!writable)
+ return -EOPNOTSUPP;
+
+ hva += offset_in_page(gpa);
+ switch (len) {
+ case 1: {
+ u8 old;
+
+ ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
+ *success = !ret && old == *old_addr;
+ *old_addr = old;
+ break;
+ }
+ case 2: {
+ u16 old;
+
+ ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
+ *success = !ret && old == *old_addr;
+ *old_addr = old;
+ break;
+ }
+ case 4: {
+ u32 old;
+
+ ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
+ *success = !ret && old == *old_addr;
+ *old_addr = old;
+ break;
+ }
+ case 8: {
+ u64 old;
+
+ ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
+ *success = !ret && old == *old_addr;
+ *old_addr = old;
+ break;
+ }
+ case 16: {
+ __uint128_t old;
+
+ ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
+ *success = !ret && old == *old_addr;
+ *old_addr = old;
+ break;
+ }
+ default:
+ return -EINVAL;
+ }
+ mark_page_dirty_in_slot(kvm, slot, gfn);
+ /*
+ * Assume that the fault is caused by protection, either key protection
+ * or user page write protection.
+ */
+ if (ret == -EFAULT)
+ ret = PGM_PROTECTION;
+ return ret;
+}
+
/**
* guest_translate_address_with_key - translate guest logical into guest absolute address
* @vcpu: virtual cpu
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 4b8b41be7aed..86e9734d5782 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -584,7 +584,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_S390_VCPU_RESETS:
case KVM_CAP_SET_GUEST_DEBUG:
case KVM_CAP_S390_DIAG318:
- case KVM_CAP_S390_MEM_OP_EXTENSION:
r = 1;
break;
case KVM_CAP_SET_GUEST_DEBUG2:
@@ -598,6 +597,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_S390_MEM_OP:
r = MEM_OP_MAX_SIZE;
break;
+ case KVM_CAP_S390_MEM_OP_EXTENSION:
+ /*
+ * Flag bits indicating which extensions are supported.
+ * If r > 0, the base extension must also be supported/indicated,
+ * in order to maintain backwards compatibility.
+ */
+ r = KVM_S390_MEMOP_EXTENSION_CAP_BASE |
+ KVM_S390_MEMOP_EXTENSION_CAP_CMPXCHG;
+ break;
case KVM_CAP_NR_VCPUS:
case KVM_CAP_MAX_VCPUS:
case KVM_CAP_MAX_VCPU_ID:
@@ -2840,6 +2848,50 @@ static int kvm_s390_vm_mem_op_abs(struct kvm *kvm, struct kvm_s390_mem_op *mop)
return r;
}
+static int kvm_s390_vm_mem_op_cmpxchg(struct kvm *kvm, struct kvm_s390_mem_op *mop)
+{
+ void __user *uaddr = (void __user *)mop->buf;
+ void __user *old_addr = (void __user *)mop->old_addr;
+ union {
+ __uint128_t quad;
+ char raw[sizeof(__uint128_t)];
+ } old = { .quad = 0}, new = { .quad = 0 };
+ unsigned int off_in_quad = sizeof(new) - mop->size;
+ int r, srcu_idx;
+ bool success;
+
+ r = mem_op_validate_common(mop, KVM_S390_MEMOP_F_SKEY_PROTECTION);
+ if (r)
+ return r;
+ /*
+ * This validates off_in_quad. Checking that size is a power
+ * of two is not necessary, as cmpxchg_guest_abs_with_key
+ * takes care of that
+ */
+ if (mop->size > sizeof(new))
+ return -EINVAL;
+ if (copy_from_user(&new.raw[off_in_quad], uaddr, mop->size))
+ return -EFAULT;
+ if (copy_from_user(&old.raw[off_in_quad], old_addr, mop->size))
+ return -EFAULT;
+
+ srcu_idx = srcu_read_lock(&kvm->srcu);
+
+ if (kvm_is_error_gpa(kvm, mop->gaddr)) {
+ r = PGM_ADDRESSING;
+ goto out_unlock;
+ }
+
+ r = cmpxchg_guest_abs_with_key(kvm, mop->gaddr, mop->size, &old.quad,
+ new.quad, mop->key, &success);
+ if (!success && copy_to_user(old_addr, &old.raw[off_in_quad], mop->size))
+ r = -EFAULT;
+
+out_unlock:
+ srcu_read_unlock(&kvm->srcu, srcu_idx);
+ return r;
+}
+
static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
{
/*
@@ -2858,6 +2910,8 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
case KVM_S390_MEMOP_ABSOLUTE_READ:
case KVM_S390_MEMOP_ABSOLUTE_WRITE:
return kvm_s390_vm_mem_op_abs(kvm, mop);
+ case KVM_S390_MEMOP_ABSOLUTE_CMPXCHG:
+ return kvm_s390_vm_mem_op_cmpxchg(kvm, mop);
default:
return -EINVAL;
}
--
2.34.1Hi Janis,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on kvm/queue]
[also build test ERROR on lwn/docs-next linus/master v6.2-rc5 next-20230127]
[cannot apply to kvms390/next kvm/linux-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Janis-Schoetterl-Glausch/KVM-s390-selftest-memop-Pass-mop_desc-via-pointer/20230128-132603
base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
patch link: https://lore.kernel.org/r/20230125212608.1860251-13-scgl%40linux.ibm.com
patch subject: [PATCH v6 12/14] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg
config: s390-randconfig-r044-20230123 (https://download.01.org/0day-ci/archive/20230128/202301282223.YafIuB1E-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 4196ca3278f78c6e19246e54ab0ecb364e37d66a)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install s390 cross compiling tool for clang build
# apt-get install binutils-s390x-linux-gnu
# https://github.com/intel-lab-lkp/linux/commit/6e6b3d99b9978a70b148b989d46b039feda3a3c3
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Janis-Schoetterl-Glausch/KVM-s390-selftest-memop-Pass-mop_desc-via-pointer/20230128-132603
git checkout 6e6b3d99b9978a70b148b989d46b039feda3a3c3
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash arch/s390/kvm/
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
In file included from arch/s390/kvm/gaccess.c:16:
In file included from arch/s390/kvm/kvm-s390.h:17:
In file included from include/linux/kvm_host.h:19:
In file included from include/linux/msi.h:27:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/s390/include/asm/io.h:75:
include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __raw_readb(PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
~~~~~~~~~~ ^
include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
#define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
^
include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
#define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
^
In file included from arch/s390/kvm/gaccess.c:16:
In file included from arch/s390/kvm/kvm-s390.h:17:
In file included from include/linux/kvm_host.h:19:
In file included from include/linux/msi.h:27:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/s390/include/asm/io.h:75:
include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
~~~~~~~~~~ ^
include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
#define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
^
include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
#define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
^
In file included from arch/s390/kvm/gaccess.c:16:
In file included from arch/s390/kvm/kvm-s390.h:17:
In file included from include/linux/kvm_host.h:19:
In file included from include/linux/msi.h:27:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/s390/include/asm/io.h:75:
include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writeb(value, PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:692:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
readsb(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:700:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
readsw(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:708:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
readsl(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:717:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
writesb(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:726:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
writesw(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:735:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
writesl(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
>> arch/s390/kvm/gaccess.c:1217:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1217:9: note: did you mean 'copy_to_user_key'?
arch/s390/include/asm/uaccess.h:51:1: note: 'copy_to_user_key' declared here
copy_to_user_key(void __user *to, const void *from, unsigned long n, unsigned long key)
^
arch/s390/kvm/gaccess.c:1225:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1233:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1241:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1249:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
^
12 warnings and 5 errors generated.
vim +/cmpxchg_user_key +1217 arch/s390/kvm/gaccess.c
1163
1164 /**
1165 * cmpxchg_guest_abs_with_key() - Perform cmpxchg on guest absolute address.
1166 * @kvm: Virtual machine instance.
1167 * @gpa: Absolute guest address of the location to be changed.
1168 * @len: Operand length of the cmpxchg, required: 1 <= len <= 16. Providing a
1169 * non power of two will result in failure.
1170 * @old_addr: Pointer to old value. If the location at @gpa contains this value,
1171 * the exchange will succeed. After calling cmpxchg_guest_abs_with_key()
1172 * *@old_addr contains the value at @gpa before the attempt to
1173 * exchange the value.
1174 * @new: The value to place at @gpa.
1175 * @access_key: The access key to use for the guest access.
1176 * @success: output value indicating if an exchange occurred.
1177 *
1178 * Atomically exchange the value at @gpa by @new, if it contains *@old.
1179 * Honors storage keys.
1180 *
1181 * Return: * 0: successful exchange
1182 * * a program interruption code indicating the reason cmpxchg could
1183 * not be attempted
1184 * * -EINVAL: address misaligned or len not power of two
1185 * * -EAGAIN: transient failure (len 1 or 2)
1186 * * -EOPNOTSUPP: read-only memslot (should never occur)
1187 */
1188 int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
1189 __uint128_t *old_addr, __uint128_t new,
1190 u8 access_key, bool *success)
1191 {
1192 gfn_t gfn = gpa >> PAGE_SHIFT;
1193 struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
1194 bool writable;
1195 hva_t hva;
1196 int ret;
1197
1198 if (!IS_ALIGNED(gpa, len))
1199 return -EINVAL;
1200
1201 hva = gfn_to_hva_memslot_prot(slot, gfn, &writable);
1202 if (kvm_is_error_hva(hva))
1203 return PGM_ADDRESSING;
1204 /*
1205 * Check if it's a read-only memslot, even though that cannot occur
1206 * since those are unsupported.
1207 * Don't try to actually handle that case.
1208 */
1209 if (!writable)
1210 return -EOPNOTSUPP;
1211
1212 hva += offset_in_page(gpa);
1213 switch (len) {
1214 case 1: {
1215 u8 old;
1216
> 1217 ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
1218 *success = !ret && old == *old_addr;
1219 *old_addr = old;
1220 break;
1221 }
1222 case 2: {
1223 u16 old;
1224
1225 ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
1226 *success = !ret && old == *old_addr;
1227 *old_addr = old;
1228 break;
1229 }
1230 case 4: {
1231 u32 old;
1232
1233 ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
1234 *success = !ret && old == *old_addr;
1235 *old_addr = old;
1236 break;
1237 }
1238 case 8: {
1239 u64 old;
1240
1241 ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
1242 *success = !ret && old == *old_addr;
1243 *old_addr = old;
1244 break;
1245 }
1246 case 16: {
1247 __uint128_t old;
1248
1249 ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
1250 *success = !ret && old == *old_addr;
1251 *old_addr = old;
1252 break;
1253 }
1254 default:
1255 return -EINVAL;
1256 }
1257 mark_page_dirty_in_slot(kvm, slot, gfn);
1258 /*
1259 * Assume that the fault is caused by protection, either key protection
1260 * or user page write protection.
1261 */
1262 if (ret == -EFAULT)
1263 ret = PGM_PROTECTION;
1264 return ret;
1265 }
1266
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests
Hi Janis,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on kvm/queue]
[also build test ERROR on lwn/docs-next linus/master v6.2-rc5 next-20230127]
[cannot apply to kvms390/next kvm/linux-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Janis-Schoetterl-Glausch/KVM-s390-selftest-memop-Pass-mop_desc-via-pointer/20230128-132603
base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
patch link: https://lore.kernel.org/r/20230125212608.1860251-13-scgl%40linux.ibm.com
patch subject: [PATCH v6 12/14] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg
config: s390-randconfig-r022-20230123 (https://download.01.org/0day-ci/archive/20230128/202301282258.RvVJOYVA-lkp@intel.com/config)
compiler: clang version 16.0.0 (https://github.com/llvm/llvm-project 4196ca3278f78c6e19246e54ab0ecb364e37d66a)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install s390 cross compiling tool for clang build
# apt-get install binutils-s390x-linux-gnu
# https://github.com/intel-lab-lkp/linux/commit/6e6b3d99b9978a70b148b989d46b039feda3a3c3
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Janis-Schoetterl-Glausch/KVM-s390-selftest-memop-Pass-mop_desc-via-pointer/20230128-132603
git checkout 6e6b3d99b9978a70b148b989d46b039feda3a3c3
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash arch/s390/kvm/
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
In file included from arch/s390/kvm/gaccess.c:16:
In file included from arch/s390/kvm/kvm-s390.h:17:
In file included from include/linux/kvm_host.h:19:
In file included from include/linux/msi.h:27:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/s390/include/asm/io.h:75:
include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __raw_readb(PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
~~~~~~~~~~ ^
include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
#define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
^
include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
#define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
^
In file included from arch/s390/kvm/gaccess.c:16:
In file included from arch/s390/kvm/kvm-s390.h:17:
In file included from include/linux/kvm_host.h:19:
In file included from include/linux/msi.h:27:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/s390/include/asm/io.h:75:
include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
~~~~~~~~~~ ^
include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
#define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
^
include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
#define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
^
In file included from arch/s390/kvm/gaccess.c:16:
In file included from arch/s390/kvm/kvm-s390.h:17:
In file included from include/linux/kvm_host.h:19:
In file included from include/linux/msi.h:27:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/s390/include/asm/io.h:75:
include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writeb(value, PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
__raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
~~~~~~~~~~ ^
include/asm-generic/io.h:692:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
readsb(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:700:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
readsw(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:708:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
readsl(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:717:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
writesb(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:726:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
writesw(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
include/asm-generic/io.h:735:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
writesl(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
>> arch/s390/kvm/gaccess.c:1217:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1217:9: note: did you mean 'copy_to_user_key'?
arch/s390/include/asm/uaccess.h:51:1: note: 'copy_to_user_key' declared here
copy_to_user_key(void __user *to, const void *from, unsigned long n, unsigned long key)
^
arch/s390/kvm/gaccess.c:1225:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1233:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1241:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
^
arch/s390/kvm/gaccess.c:1249:9: error: call to undeclared function 'cmpxchg_user_key'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
^
12 warnings and 5 errors generated.
vim +/cmpxchg_user_key +1217 arch/s390/kvm/gaccess.c
1163
1164 /**
1165 * cmpxchg_guest_abs_with_key() - Perform cmpxchg on guest absolute address.
1166 * @kvm: Virtual machine instance.
1167 * @gpa: Absolute guest address of the location to be changed.
1168 * @len: Operand length of the cmpxchg, required: 1 <= len <= 16. Providing a
1169 * non power of two will result in failure.
1170 * @old_addr: Pointer to old value. If the location at @gpa contains this value,
1171 * the exchange will succeed. After calling cmpxchg_guest_abs_with_key()
1172 * *@old_addr contains the value at @gpa before the attempt to
1173 * exchange the value.
1174 * @new: The value to place at @gpa.
1175 * @access_key: The access key to use for the guest access.
1176 * @success: output value indicating if an exchange occurred.
1177 *
1178 * Atomically exchange the value at @gpa by @new, if it contains *@old.
1179 * Honors storage keys.
1180 *
1181 * Return: * 0: successful exchange
1182 * * a program interruption code indicating the reason cmpxchg could
1183 * not be attempted
1184 * * -EINVAL: address misaligned or len not power of two
1185 * * -EAGAIN: transient failure (len 1 or 2)
1186 * * -EOPNOTSUPP: read-only memslot (should never occur)
1187 */
1188 int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
1189 __uint128_t *old_addr, __uint128_t new,
1190 u8 access_key, bool *success)
1191 {
1192 gfn_t gfn = gpa >> PAGE_SHIFT;
1193 struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
1194 bool writable;
1195 hva_t hva;
1196 int ret;
1197
1198 if (!IS_ALIGNED(gpa, len))
1199 return -EINVAL;
1200
1201 hva = gfn_to_hva_memslot_prot(slot, gfn, &writable);
1202 if (kvm_is_error_hva(hva))
1203 return PGM_ADDRESSING;
1204 /*
1205 * Check if it's a read-only memslot, even though that cannot occur
1206 * since those are unsupported.
1207 * Don't try to actually handle that case.
1208 */
1209 if (!writable)
1210 return -EOPNOTSUPP;
1211
1212 hva += offset_in_page(gpa);
1213 switch (len) {
1214 case 1: {
1215 u8 old;
1216
> 1217 ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
1218 *success = !ret && old == *old_addr;
1219 *old_addr = old;
1220 break;
1221 }
1222 case 2: {
1223 u16 old;
1224
1225 ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
1226 *success = !ret && old == *old_addr;
1227 *old_addr = old;
1228 break;
1229 }
1230 case 4: {
1231 u32 old;
1232
1233 ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
1234 *success = !ret && old == *old_addr;
1235 *old_addr = old;
1236 break;
1237 }
1238 case 8: {
1239 u64 old;
1240
1241 ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
1242 *success = !ret && old == *old_addr;
1243 *old_addr = old;
1244 break;
1245 }
1246 case 16: {
1247 __uint128_t old;
1248
1249 ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
1250 *success = !ret && old == *old_addr;
1251 *old_addr = old;
1252 break;
1253 }
1254 default:
1255 return -EINVAL;
1256 }
1257 mark_page_dirty_in_slot(kvm, slot, gfn);
1258 /*
1259 * Assume that the fault is caused by protection, either key protection
1260 * or user page write protection.
1261 */
1262 if (ret == -EFAULT)
1263 ret = PGM_PROTECTION;
1264 return ret;
1265 }
1266
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests
Hi Janis,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on kvm/queue]
[also build test ERROR on lwn/docs-next linus/master]
[cannot apply to kvms390/next kvm/linux-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Janis-Schoetterl-Glausch/KVM-s390-selftest-memop-Pass-mop_desc-via-pointer/20230128-132603
base: https://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
patch link: https://lore.kernel.org/r/20230125212608.1860251-13-scgl%40linux.ibm.com
patch subject: [PATCH v6 12/14] KVM: s390: Extend MEM_OP ioctl by storage key checked cmpxchg
config: s390-allyesconfig (https://download.01.org/0day-ci/archive/20230128/202301281752.6gSopuWh-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/6e6b3d99b9978a70b148b989d46b039feda3a3c3
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Janis-Schoetterl-Glausch/KVM-s390-selftest-memop-Pass-mop_desc-via-pointer/20230128-132603
git checkout 6e6b3d99b9978a70b148b989d46b039feda3a3c3
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
All errors (new ones prefixed by >>):
arch/s390/kvm/gaccess.c: In function 'cmpxchg_guest_abs_with_key':
>> arch/s390/kvm/gaccess.c:1217:23: error: implicit declaration of function 'cmpxchg_user_key'; did you mean 'copy_to_user_key'? [-Werror=implicit-function-declaration]
1217 | ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
| ^~~~~~~~~~~~~~~~
| copy_to_user_key
cc1: some warnings being treated as errors
vim +1217 arch/s390/kvm/gaccess.c
1163
1164 /**
1165 * cmpxchg_guest_abs_with_key() - Perform cmpxchg on guest absolute address.
1166 * @kvm: Virtual machine instance.
1167 * @gpa: Absolute guest address of the location to be changed.
1168 * @len: Operand length of the cmpxchg, required: 1 <= len <= 16. Providing a
1169 * non power of two will result in failure.
1170 * @old_addr: Pointer to old value. If the location at @gpa contains this value,
1171 * the exchange will succeed. After calling cmpxchg_guest_abs_with_key()
1172 * *@old_addr contains the value at @gpa before the attempt to
1173 * exchange the value.
1174 * @new: The value to place at @gpa.
1175 * @access_key: The access key to use for the guest access.
1176 * @success: output value indicating if an exchange occurred.
1177 *
1178 * Atomically exchange the value at @gpa by @new, if it contains *@old.
1179 * Honors storage keys.
1180 *
1181 * Return: * 0: successful exchange
1182 * * a program interruption code indicating the reason cmpxchg could
1183 * not be attempted
1184 * * -EINVAL: address misaligned or len not power of two
1185 * * -EAGAIN: transient failure (len 1 or 2)
1186 * * -EOPNOTSUPP: read-only memslot (should never occur)
1187 */
1188 int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
1189 __uint128_t *old_addr, __uint128_t new,
1190 u8 access_key, bool *success)
1191 {
1192 gfn_t gfn = gpa >> PAGE_SHIFT;
1193 struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
1194 bool writable;
1195 hva_t hva;
1196 int ret;
1197
1198 if (!IS_ALIGNED(gpa, len))
1199 return -EINVAL;
1200
1201 hva = gfn_to_hva_memslot_prot(slot, gfn, &writable);
1202 if (kvm_is_error_hva(hva))
1203 return PGM_ADDRESSING;
1204 /*
1205 * Check if it's a read-only memslot, even though that cannot occur
1206 * since those are unsupported.
1207 * Don't try to actually handle that case.
1208 */
1209 if (!writable)
1210 return -EOPNOTSUPP;
1211
1212 hva += offset_in_page(gpa);
1213 switch (len) {
1214 case 1: {
1215 u8 old;
1216
> 1217 ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
1218 *success = !ret && old == *old_addr;
1219 *old_addr = old;
1220 break;
1221 }
1222 case 2: {
1223 u16 old;
1224
1225 ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
1226 *success = !ret && old == *old_addr;
1227 *old_addr = old;
1228 break;
1229 }
1230 case 4: {
1231 u32 old;
1232
1233 ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
1234 *success = !ret && old == *old_addr;
1235 *old_addr = old;
1236 break;
1237 }
1238 case 8: {
1239 u64 old;
1240
1241 ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
1242 *success = !ret && old == *old_addr;
1243 *old_addr = old;
1244 break;
1245 }
1246 case 16: {
1247 __uint128_t old;
1248
1249 ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
1250 *success = !ret && old == *old_addr;
1251 *old_addr = old;
1252 break;
1253 }
1254 default:
1255 return -EINVAL;
1256 }
1257 mark_page_dirty_in_slot(kvm, slot, gfn);
1258 /*
1259 * Assume that the fault is caused by protection, either key protection
1260 * or user page write protection.
1261 */
1262 if (ret == -EFAULT)
1263 ret = PGM_PROTECTION;
1264 return ret;
1265 }
1266
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests
On 1/25/23 22:26, Janis Schoetterl-Glausch wrote:
> User space can use the MEM_OP ioctl to make storage key checked reads
> and writes to the guest, however, it has no way of performing atomic,
> key checked, accesses to the guest.
> Extend the MEM_OP ioctl in order to allow for this, by adding a cmpxchg
> op. For now, support this op for absolute accesses only.
>
> This op can be use, for example, to set the device-state-change
s/use/used/
> indicator and the adapter-local-summary indicator atomically.
>
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> ---
[...]
> +/**
> + * cmpxchg_guest_abs_with_key() - Perform cmpxchg on guest absolute address.
> + * @kvm: Virtual machine instance.
> + * @gpa: Absolute guest address of the location to be changed.
> + * @len: Operand length of the cmpxchg, required: 1 <= len <= 16. Providing a
> + * non power of two will result in failure.
> + * @old_addr: Pointer to old value. If the location at @gpa contains this value,
> + * the exchange will succeed. After calling cmpxchg_guest_abs_with_key()
> + * *@old_addr contains the value at @gpa before the attempt to
> + * exchange the value.
> + * @new: The value to place at @gpa.
> + * @access_key: The access key to use for the guest access.
> + * @success: output value indicating if an exchange occurred.
> + *
> + * Atomically exchange the value at @gpa by @new, if it contains *@old.
> + * Honors storage keys.
> + *
> + * Return: * 0: successful exchange
> + * * a program interruption code indicating the reason cmpxchg could
> + * not be attempted
Nit:
>0: a program interruption code...
> + * * -EINVAL: address misaligned or len not power of two
> + * * -EAGAIN: transient failure (len 1 or 2)
> + * * -EOPNOTSUPP: read-only memslot (should never occur)
> + */
> +int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
> + __uint128_t *old_addr, __uint128_t new,
> + u8 access_key, bool *success)
> +{
> + gfn_t gfn = gpa >> PAGE_SHIFT;
gpa_to_gfn()?
> + struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
> + bool writable;
> + hva_t hva;
> + int ret;
> +
> + if (!IS_ALIGNED(gpa, len))
> + return -EINVAL;
> +
> + hva = gfn_to_hva_memslot_prot(slot, gfn, &writable);
> + if (kvm_is_error_hva(hva))
> + return PGM_ADDRESSING;
> + /*
> + * Check if it's a read-only memslot, even though that cannot occur
> + * since those are unsupported.
> + * Don't try to actually handle that case.
> + */
> + if (!writable)
> + return -EOPNOTSUPP;
> +
> + hva += offset_in_page(gpa);
Hmm if we don't use a macro to generate these then I'd add an explanation:
cmpxchg_user_key() is a macro that is dependent on the type of "old" so
there's no deduplication possible without further macros.
> + switch (len) {
> + case 1: {
> + u8 old;
> +
> + ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
> + *success = !ret && old == *old_addr;
> + *old_addr = old;
> + break;
> + }
> + case 2: {
> + u16 old;
> +
> + ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
> + *success = !ret && old == *old_addr;
> + *old_addr = old;
> + break;
> + }
> + case 4: {
> + u32 old;
> +
> + ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
> + *success = !ret && old == *old_addr;
> + *old_addr = old;
> + break;
> + }
> + case 8: {
> + u64 old;
> +
> + ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
> + *success = !ret && old == *old_addr;
> + *old_addr = old;
> + break;
> + }
> + case 16: {
> + __uint128_t old;
> +
> + ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
> + *success = !ret && old == *old_addr;
> + *old_addr = old;
> + break;
> + }
> + default:
> + return -EINVAL;
> + }
> + mark_page_dirty_in_slot(kvm, slot, gfn);
Is that needed if we failed the store?
> + /*
> + * Assume that the fault is caused by protection, either key protection
> + * or user page write protection.
> + */
> + if (ret == -EFAULT)
> + ret = PGM_PROTECTION;
> + return ret;
> +}
> +
> /**
> * guest_translate_address_with_key - translate guest logical into guest absolute address
> * @vcpu: virtual cpu
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 4b8b41be7aed..86e9734d5782 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -584,7 +584,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_S390_VCPU_RESETS:
> case KVM_CAP_SET_GUEST_DEBUG:
> case KVM_CAP_S390_DIAG318:
> - case KVM_CAP_S390_MEM_OP_EXTENSION:
> r = 1;
> break;
> case KVM_CAP_SET_GUEST_DEBUG2:
> @@ -598,6 +597,15 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_S390_MEM_OP:
> r = MEM_OP_MAX_SIZE;
> break;
> + case KVM_CAP_S390_MEM_OP_EXTENSION:
> + /*
> + * Flag bits indicating which extensions are supported.
> + * If r > 0, the base extension must also be supported/indicated,
> + * in order to maintain backwards compatibility.
> + */
> + r = KVM_S390_MEMOP_EXTENSION_CAP_BASE |
> + KVM_S390_MEMOP_EXTENSION_CAP_CMPXCHG;
> + break;
> case KVM_CAP_NR_VCPUS:
> case KVM_CAP_MAX_VCPUS:
> case KVM_CAP_MAX_VCPU_ID:
> @@ -2840,6 +2848,50 @@ static int kvm_s390_vm_mem_op_abs(struct kvm *kvm, struct kvm_s390_mem_op *mop)
> return r;
> }
>
> +static int kvm_s390_vm_mem_op_cmpxchg(struct kvm *kvm, struct kvm_s390_mem_op *mop)
> +{
> + void __user *uaddr = (void __user *)mop->buf;
> + void __user *old_addr = (void __user *)mop->old_addr;
> + union {
> + __uint128_t quad;
> + char raw[sizeof(__uint128_t)];
> + } old = { .quad = 0}, new = { .quad = 0 };
> + unsigned int off_in_quad = sizeof(new) - mop->size;
> + int r, srcu_idx;
> + bool success;
> +
> + r = mem_op_validate_common(mop, KVM_S390_MEMOP_F_SKEY_PROTECTION);
> + if (r)
> + return r;
> + /*
> + * This validates off_in_quad. Checking that size is a power
> + * of two is not necessary, as cmpxchg_guest_abs_with_key
> + * takes care of that
> + */
> + if (mop->size > sizeof(new))
> + return -EINVAL;
> + if (copy_from_user(&new.raw[off_in_quad], uaddr, mop->size))
> + return -EFAULT;
> + if (copy_from_user(&old.raw[off_in_quad], old_addr, mop->size))
> + return -EFAULT;
> +
> + srcu_idx = srcu_read_lock(&kvm->srcu);
> +
> + if (kvm_is_error_gpa(kvm, mop->gaddr)) {
> + r = PGM_ADDRESSING;
> + goto out_unlock;
> + }
> +
> + r = cmpxchg_guest_abs_with_key(kvm, mop->gaddr, mop->size, &old.quad,
> + new.quad, mop->key, &success);
> + if (!success && copy_to_user(old_addr, &old.raw[off_in_quad], mop->size))
> + r = -EFAULT;
> +
> +out_unlock:
> + srcu_read_unlock(&kvm->srcu, srcu_idx);
> + return r;
> +}
> +
> static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
> {
> /*
> @@ -2858,6 +2910,8 @@ static int kvm_s390_vm_mem_op(struct kvm *kvm, struct kvm_s390_mem_op *mop)
> case KVM_S390_MEMOP_ABSOLUTE_READ:
> case KVM_S390_MEMOP_ABSOLUTE_WRITE:
> return kvm_s390_vm_mem_op_abs(kvm, mop);
> + case KVM_S390_MEMOP_ABSOLUTE_CMPXCHG:
> + return kvm_s390_vm_mem_op_cmpxchg(kvm, mop);
> default:
> return -EINVAL;
> }
On Thu, 2023-01-26 at 17:10 +0100, Janosch Frank wrote:
> On 1/25/23 22:26, Janis Schoetterl-Glausch wrote:
> > User space can use the MEM_OP ioctl to make storage key checked reads
> > and writes to the guest, however, it has no way of performing atomic,
> > key checked, accesses to the guest.
> > Extend the MEM_OP ioctl in order to allow for this, by adding a cmpxchg
> > op. For now, support this op for absolute accesses only.
> >
> > This op can be use, for example, to set the device-state-change
>
> s/use/used/
>
> > indicator and the adapter-local-summary indicator atomically.
> >
> > Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> > ---
> [...]
> > +/**
> > + * cmpxchg_guest_abs_with_key() - Perform cmpxchg on guest absolute address.
> > + * @kvm: Virtual machine instance.
> > + * @gpa: Absolute guest address of the location to be changed.
> > + * @len: Operand length of the cmpxchg, required: 1 <= len <= 16. Providing a
> > + * non power of two will result in failure.
> > + * @old_addr: Pointer to old value. If the location at @gpa contains this value,
> > + * the exchange will succeed. After calling cmpxchg_guest_abs_with_key()
> > + * *@old_addr contains the value at @gpa before the attempt to
> > + * exchange the value.
> > + * @new: The value to place at @gpa.
> > + * @access_key: The access key to use for the guest access.
> > + * @success: output value indicating if an exchange occurred.
> > + *
> > + * Atomically exchange the value at @gpa by @new, if it contains *@old.
> > + * Honors storage keys.
> > + *
> > + * Return: * 0: successful exchange
> > + * * a program interruption code indicating the reason cmpxchg could
> > + * not be attempted
>
> Nit:
> >0: a program interruption code...
>
>
> > + * * -EINVAL: address misaligned or len not power of two
> > + * * -EAGAIN: transient failure (len 1 or 2)
> > + * * -EOPNOTSUPP: read-only memslot (should never occur)
> > + */
> > +int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len,
> > + __uint128_t *old_addr, __uint128_t new,
> > + u8 access_key, bool *success)
> > +{
> > + gfn_t gfn = gpa >> PAGE_SHIFT;
>
> gpa_to_gfn()?
Yes.
>
> > + struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
> > + bool writable;
> > + hva_t hva;
> > + int ret;
> > +
> > + if (!IS_ALIGNED(gpa, len))
> > + return -EINVAL;
> > +
> > + hva = gfn_to_hva_memslot_prot(slot, gfn, &writable);
> > + if (kvm_is_error_hva(hva))
> > + return PGM_ADDRESSING;
> > + /*
> > + * Check if it's a read-only memslot, even though that cannot occur
> > + * since those are unsupported.
> > + * Don't try to actually handle that case.
> > + */
> > + if (!writable)
> > + return -EOPNOTSUPP;
> > +
> > + hva += offset_in_page(gpa);
>
> Hmm if we don't use a macro to generate these then I'd add an explanation:
>
> cmpxchg_user_key() is a macro that is dependent on the type of "old" so
> there's no deduplication possible without further macros.
Can do.
Btw. I could move the other two statements out of the switch by using a union of old values,
memcmp and memcpy, but I think that would be less readable.
>
> > + switch (len) {
> > + case 1: {
> > + u8 old;
> > +
> > + ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key);
> > + *success = !ret && old == *old_addr;
> > + *old_addr = old;
> > + break;
> > + }
> > + case 2: {
> > + u16 old;
> > +
> > + ret = cmpxchg_user_key((u16 *)hva, &old, *old_addr, new, access_key);
> > + *success = !ret && old == *old_addr;
> > + *old_addr = old;
> > + break;
> > + }
> > + case 4: {
> > + u32 old;
> > +
> > + ret = cmpxchg_user_key((u32 *)hva, &old, *old_addr, new, access_key);
> > + *success = !ret && old == *old_addr;
> > + *old_addr = old;
> > + break;
> > + }
> > + case 8: {
> > + u64 old;
> > +
> > + ret = cmpxchg_user_key((u64 *)hva, &old, *old_addr, new, access_key);
> > + *success = !ret && old == *old_addr;
> > + *old_addr = old;
> > + break;
> > + }
> > + case 16: {
> > + __uint128_t old;
> > +
> > + ret = cmpxchg_user_key((__uint128_t *)hva, &old, *old_addr, new, access_key);
> > + *success = !ret && old == *old_addr;
> > + *old_addr = old;
> > + break;
> > + }
> > + default:
> > + return -EINVAL;
> > + }
> > + mark_page_dirty_in_slot(kvm, slot, gfn);
>
> Is that needed if we failed the store?
Indeed it isn't.
[...]
On Wed, Jan 25, 2023 at 10:26:06PM +0100, Janis Schoetterl-Glausch wrote: > User space can use the MEM_OP ioctl to make storage key checked reads > and writes to the guest, however, it has no way of performing atomic, > key checked, accesses to the guest. > Extend the MEM_OP ioctl in order to allow for this, by adding a cmpxchg > op. For now, support this op for absolute accesses only. > > This op can be use, for example, to set the device-state-change > indicator and the adapter-local-summary indicator atomically. > > Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com> > --- > include/uapi/linux/kvm.h | 8 +++ > arch/s390/kvm/gaccess.h | 3 ++ > arch/s390/kvm/gaccess.c | 103 +++++++++++++++++++++++++++++++++++++++ > arch/s390/kvm/kvm-s390.c | 56 ++++++++++++++++++++- > 4 files changed, 169 insertions(+), 1 deletion(-) ... > + ret = cmpxchg_user_key((u8 *)hva, &old, *old_addr, new, access_key); FWIW, this and the three others need a __user annotation: ret = cmpxchg_user_key((u8 __user *)hva, &old, *old_addr, new, access_key); Otherwise you end up with sparse warnings (compile with C=1).
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