target/i386/cpu.h | 3 +++ target/i386/kvm/kvm.c | 15 +++++++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-)
The kvm_arch_get_supported_cpuid() only call KVM_GET_SUPPORTED_CPUID one
time, so the cpuid buffer information still keep older value. Once Qemu
enable new dynamic xfeature, like XTILEDATA, the cpuid[0D,0].{EBX,ECX}
still return older value.
This patch can return right size value in kvm_init_xsave() if XTILEDATA
has been enabled by arch_prctl.
assert(kvm_arch_get_supported_cpuid(kvm_state, 0xd, 0, R_ECX) <=
env->xsave_buf_len);
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
---
target/i386/cpu.h | 3 +++
target/i386/kvm/kvm.c | 15 +++++++++++++--
2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 5e406088a9..814ba4020b 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -565,6 +565,9 @@ typedef enum X86Seg {
#define ESA_FEATURE_ALIGN64_MASK (1U << ESA_FEATURE_ALIGN64_BIT)
#define ESA_FEATURE_XFD_MASK (1U << ESA_FEATURE_XFD_BIT)
+#define ARCH_GET_XCOMP_GUEST_PERM 0x1024
+#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025
+
/* CPUID feature words */
typedef enum FeatureWord {
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index 06901c2a43..312d4fccf8 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -46,6 +46,7 @@
#include "hw/i386/intel_iommu.h"
#include "hw/i386/x86-iommu.h"
#include "hw/i386/e820_memory_layout.h"
+#include "target/i386/cpu.h"
#include "hw/pci/pci.h"
#include "hw/pci/msi.h"
@@ -437,6 +438,18 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
return ret;
}
ret = (reg == R_EAX) ? bitmask : bitmask >> 32;
+ } else if (function == 0xd && index == 0 &&
+ (reg == R_EBX || reg == R_ECX)) {
+ /*
+ * The value returned by KVM_GET_SUPPORTED_CPUID does not include
+ * features that already be enabled with the arch_prctl system call.
+ */
+ int rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_GUEST_PERM, &bitmask);
+ if (rc) {
+ warn_report("prctl(ARCH_GET_XCOMP_GUEST_PERM) error: %d", rc);
+ } else if (bitmask & XSTATE_XTILE_DATA_MASK) {
+ ret += sizeof(XSaveXTILEDATA);
+ }
} else if (function == 0x80000001 && reg == R_ECX) {
/*
* It's safe to enable TOPOEXT even if it's not returned by
@@ -5214,8 +5227,6 @@ bool kvm_arch_cpu_check_are_resettable(void)
return !sev_es_enabled();
}
-#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025
-
void kvm_request_xsave_components(X86CPU *cpu, uint64_t mask)
{
KVMState *s = kvm_state;
On 3/24/22 04:18, Yang Zhong wrote: > The kvm_arch_get_supported_cpuid() only call KVM_GET_SUPPORTED_CPUID one > time, so the cpuid buffer information still keep older value. Once Qemu > enable new dynamic xfeature, like XTILEDATA, the cpuid[0D,0].{EBX,ECX} > still return older value. > > This patch can return right size value in kvm_init_xsave() if XTILEDATA > has been enabled by arch_prctl. > > assert(kvm_arch_get_supported_cpuid(kvm_state, 0xd, 0, R_ECX) <= > env->xsave_buf_len); > > Signed-off-by: Yang Zhong <yang.zhong@intel.com> I don't understand, is this a bugfix for an assertion failure or just a cleanup? Either way, while I like the idea of modifying kvm_arch_get_supported_cpuid, I think the right thing to do is to just use has_xsave2 as the return value if it is nonzero. And then kvm_init_xsave can just do if (!has_xsave) { return; } env->xsave_buf_len = kvm_arch_get_supported_cpuid(kvm_state, 0xd, 0, R_ECX); without the assertion that is now obvious. Paolo > --- > target/i386/cpu.h | 3 +++ > target/i386/kvm/kvm.c | 15 +++++++++++++-- > 2 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/target/i386/cpu.h b/target/i386/cpu.h > index 5e406088a9..814ba4020b 100644 > --- a/target/i386/cpu.h > +++ b/target/i386/cpu.h > @@ -565,6 +565,9 @@ typedef enum X86Seg { > #define ESA_FEATURE_ALIGN64_MASK (1U << ESA_FEATURE_ALIGN64_BIT) > #define ESA_FEATURE_XFD_MASK (1U << ESA_FEATURE_XFD_BIT) > > +#define ARCH_GET_XCOMP_GUEST_PERM 0x1024 > +#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025 > + > > /* CPUID feature words */ > typedef enum FeatureWord { > diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c > index 06901c2a43..312d4fccf8 100644 > --- a/target/i386/kvm/kvm.c > +++ b/target/i386/kvm/kvm.c > @@ -46,6 +46,7 @@ > #include "hw/i386/intel_iommu.h" > #include "hw/i386/x86-iommu.h" > #include "hw/i386/e820_memory_layout.h" > +#include "target/i386/cpu.h" > > #include "hw/pci/pci.h" > #include "hw/pci/msi.h" > @@ -437,6 +438,18 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function, > return ret; > } > ret = (reg == R_EAX) ? bitmask : bitmask >> 32; > + } else if (function == 0xd && index == 0 && > + (reg == R_EBX || reg == R_ECX)) { > + /* > + * The value returned by KVM_GET_SUPPORTED_CPUID does not include > + * features that already be enabled with the arch_prctl system call. > + */ > + int rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_GUEST_PERM, &bitmask); > + if (rc) { > + warn_report("prctl(ARCH_GET_XCOMP_GUEST_PERM) error: %d", rc); > + } else if (bitmask & XSTATE_XTILE_DATA_MASK) { > + ret += sizeof(XSaveXTILEDATA); > + } > } else if (function == 0x80000001 && reg == R_ECX) { > /* > * It's safe to enable TOPOEXT even if it's not returned by > @@ -5214,8 +5227,6 @@ bool kvm_arch_cpu_check_are_resettable(void) > return !sev_es_enabled(); > } > > -#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025 > - > void kvm_request_xsave_components(X86CPU *cpu, uint64_t mask) > { > KVMState *s = kvm_state; >
On Thu, Mar 24, 2022 at 08:35:10AM +0100, Paolo Bonzini wrote: > On 3/24/22 04:18, Yang Zhong wrote: > >The kvm_arch_get_supported_cpuid() only call KVM_GET_SUPPORTED_CPUID one > >time, so the cpuid buffer information still keep older value. Once Qemu > >enable new dynamic xfeature, like XTILEDATA, the cpuid[0D,0].{EBX,ECX} > >still return older value. > > > >This patch can return right size value in kvm_init_xsave() if XTILEDATA > >has been enabled by arch_prctl. > > > >assert(kvm_arch_get_supported_cpuid(kvm_state, 0xd, 0, R_ECX) <= > > env->xsave_buf_len); > > > >Signed-off-by: Yang Zhong <yang.zhong@intel.com> > > I don't understand, is this a bugfix for an assertion failure or > just a cleanup? > In fact, no assert issue here. The issue is after we enable dynamic xfeature, and if we still use kvm_arch_get_supported_cpuid(kvm_state, 0xd, 0, R_ECX) to get size, the size is older value(size:2816), not the size(11008) we expected. The code for cpuid[0D,0].{EBX,ECX} by kvm_arch_get_supported_cpuid() need cleanup here, or we can't get the real value here. thanks! Yang > Either way, while I like the idea of modifying > kvm_arch_get_supported_cpuid, I think the right thing to do is to > just use has_xsave2 as the return value if it is nonzero. And then > kvm_init_xsave can just do > > if (!has_xsave) { > return; > } > env->xsave_buf_len = kvm_arch_get_supported_cpuid(kvm_state, 0xd, 0, R_ECX); > > without the assertion that is now obvious. > > Paolo > > >--- > > target/i386/cpu.h | 3 +++ > > target/i386/kvm/kvm.c | 15 +++++++++++++-- > > 2 files changed, 16 insertions(+), 2 deletions(-) > > > >diff --git a/target/i386/cpu.h b/target/i386/cpu.h > >index 5e406088a9..814ba4020b 100644 > >--- a/target/i386/cpu.h > >+++ b/target/i386/cpu.h > >@@ -565,6 +565,9 @@ typedef enum X86Seg { > > #define ESA_FEATURE_ALIGN64_MASK (1U << ESA_FEATURE_ALIGN64_BIT) > > #define ESA_FEATURE_XFD_MASK (1U << ESA_FEATURE_XFD_BIT) > >+#define ARCH_GET_XCOMP_GUEST_PERM 0x1024 > >+#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025 > >+ > > /* CPUID feature words */ > > typedef enum FeatureWord { > >diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c > >index 06901c2a43..312d4fccf8 100644 > >--- a/target/i386/kvm/kvm.c > >+++ b/target/i386/kvm/kvm.c > >@@ -46,6 +46,7 @@ > > #include "hw/i386/intel_iommu.h" > > #include "hw/i386/x86-iommu.h" > > #include "hw/i386/e820_memory_layout.h" > >+#include "target/i386/cpu.h" > > #include "hw/pci/pci.h" > > #include "hw/pci/msi.h" > >@@ -437,6 +438,18 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function, > > return ret; > > } > > ret = (reg == R_EAX) ? bitmask : bitmask >> 32; > >+ } else if (function == 0xd && index == 0 && > >+ (reg == R_EBX || reg == R_ECX)) { > >+ /* > >+ * The value returned by KVM_GET_SUPPORTED_CPUID does not include > >+ * features that already be enabled with the arch_prctl system call. > >+ */ > >+ int rc = syscall(SYS_arch_prctl, ARCH_GET_XCOMP_GUEST_PERM, &bitmask); > >+ if (rc) { > >+ warn_report("prctl(ARCH_GET_XCOMP_GUEST_PERM) error: %d", rc); > >+ } else if (bitmask & XSTATE_XTILE_DATA_MASK) { > >+ ret += sizeof(XSaveXTILEDATA); > >+ } > > } else if (function == 0x80000001 && reg == R_ECX) { > > /* > > * It's safe to enable TOPOEXT even if it's not returned by > >@@ -5214,8 +5227,6 @@ bool kvm_arch_cpu_check_are_resettable(void) > > return !sev_es_enabled(); > > } > >-#define ARCH_REQ_XCOMP_GUEST_PERM 0x1025 > >- > > void kvm_request_xsave_components(X86CPU *cpu, uint64_t mask) > > { > > KVMState *s = kvm_state; > >
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