Option PARAVIRT_SPINLOCKS is added on LoongArch system, and
pv_lock_ops template is added here. If option PARAVIRT_SPINLOCKS
is enabled, the native ops works on host machine.
Two functions kvm_wait() and kvm_kick_cpu() are added specicial for
VM, if VM detects hypervisor supports pv spinlock. With kvm_wait()
vCPU thread will exit to hypervisor and give up scheduleing on pCPU,
and with function kvm_kick_cpu() one hypercall function is used
to notify hypervisor to wakeup previously waited vCPU.
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
---
arch/loongarch/Kconfig | 14 +++
arch/loongarch/include/asm/Kbuild | 1 -
arch/loongarch/include/asm/paravirt.h | 47 ++++++++++
arch/loongarch/include/asm/qspinlock.h | 39 ++++++++
.../include/asm/qspinlock_paravirt.h | 6 ++
arch/loongarch/kernel/paravirt.c | 88 +++++++++++++++++++
arch/loongarch/kernel/smp.c | 4 +-
7 files changed, 197 insertions(+), 2 deletions(-)
create mode 100644 arch/loongarch/include/asm/qspinlock.h
create mode 100644 arch/loongarch/include/asm/qspinlock_paravirt.h
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index b81d0eba5c7e..7ad63db2fafd 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -660,6 +660,20 @@ config PARAVIRT_TIME_ACCOUNTING
If in doubt, say N here.
+config PARAVIRT_SPINLOCKS
+ bool "Paravirtual queued spinlocks"
+ select PARAVIRT
+ depends on SMP
+ help
+ Paravirtualized spinlocks allow a pvops backend to replace the
+ spinlock implementation with something virtualization-friendly
+ (for example, block the virtual CPU rather than spinning).
+
+ It has a minimal impact on native kernels and gives a nice performance
+ benefit on paravirtualized kernels.
+
+ If you are unsure how to answer this question, answer Y.
+
endmenu
config ARCH_SELECT_MEMORY_MODEL
diff --git a/arch/loongarch/include/asm/Kbuild b/arch/loongarch/include/asm/Kbuild
index 2bb3676429c0..4635b755b2b4 100644
--- a/arch/loongarch/include/asm/Kbuild
+++ b/arch/loongarch/include/asm/Kbuild
@@ -6,7 +6,6 @@ generic-y += mcs_spinlock.h
generic-y += parport.h
generic-y += early_ioremap.h
generic-y += qrwlock.h
-generic-y += qspinlock.h
generic-y += user.h
generic-y += ioctl.h
generic-y += statfs.h
diff --git a/arch/loongarch/include/asm/paravirt.h b/arch/loongarch/include/asm/paravirt.h
index dddec49671ae..2617d635171b 100644
--- a/arch/loongarch/include/asm/paravirt.h
+++ b/arch/loongarch/include/asm/paravirt.h
@@ -20,6 +20,47 @@ static inline u64 paravirt_steal_clock(int cpu)
int __init pv_ipi_init(void);
int __init pv_time_init(void);
+#if defined(CONFIG_PARAVIRT_SPINLOCKS)
+struct qspinlock;
+struct pv_lock_ops {
+ void (*queued_spin_lock_slowpath)(struct qspinlock *lock, u32 val);
+ void (*queued_spin_unlock)(struct qspinlock *lock);
+ void (*wait)(u8 *ptr, u8 val);
+ void (*kick)(int cpu);
+ bool (*vcpu_is_preempted)(int cpu);
+};
+
+extern struct pv_lock_ops pv_lock_ops;
+
+void __init kvm_spinlock_init(void);
+bool pv_is_native_spin_unlock(void);
+
+static __always_inline void pv_queued_spin_lock_slowpath(struct qspinlock *lock,
+ u32 val)
+{
+ pv_lock_ops.queued_spin_lock_slowpath(lock, val);
+}
+
+static __always_inline void pv_queued_spin_unlock(struct qspinlock *lock)
+{
+ pv_lock_ops.queued_spin_unlock(lock);
+}
+
+static __always_inline void pv_wait(u8 *ptr, u8 val)
+{
+ pv_lock_ops.wait(ptr, val);
+}
+
+static __always_inline void pv_kick(int cpu)
+{
+ pv_lock_ops.kick(cpu);
+}
+
+static __always_inline bool pv_vcpu_is_preempted(long cpu)
+{
+ return pv_lock_ops.vcpu_is_preempted(cpu);
+}
+#endif /* PARAVIRT_SPINLOCKS */
#else
static inline int pv_ipi_init(void)
@@ -32,4 +73,10 @@ static inline int pv_time_init(void)
return 0;
}
#endif // CONFIG_PARAVIRT
+
+#ifndef CONFIG_PARAVIRT_SPINLOCKS
+static inline void kvm_spinlock_init(void)
+{
+}
+#endif
#endif
diff --git a/arch/loongarch/include/asm/qspinlock.h b/arch/loongarch/include/asm/qspinlock.h
new file mode 100644
index 000000000000..8e1b14c9e906
--- /dev/null
+++ b/arch/loongarch/include/asm/qspinlock.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_LOONGARCH_QSPINLOCK_H
+#define _ASM_LOONGARCH_QSPINLOCK_H
+
+#include <asm/paravirt.h>
+
+#define _Q_PENDING_LOOPS (1 << 9)
+
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+/* How long a lock should spin before we consider blocking */
+#define SPIN_THRESHOLD (1 << 15)
+
+extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
+extern void __pv_init_lock_hash(void);
+extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
+extern void __pv_queued_spin_unlock(struct qspinlock *lock);
+extern bool nopvspin;
+
+static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
+{
+ pv_queued_spin_lock_slowpath(lock, val);
+}
+
+#define queued_spin_unlock queued_spin_unlock
+static inline void queued_spin_unlock(struct qspinlock *lock)
+{
+ pv_queued_spin_unlock(lock);
+}
+
+#define vcpu_is_preempted vcpu_is_preempted
+static inline bool vcpu_is_preempted(long cpu)
+{
+ return pv_vcpu_is_preempted(cpu);
+}
+#endif
+
+#include <asm-generic/qspinlock.h>
+
+#endif // _ASM_LOONGARCH_QSPINLOCK_H
diff --git a/arch/loongarch/include/asm/qspinlock_paravirt.h b/arch/loongarch/include/asm/qspinlock_paravirt.h
new file mode 100644
index 000000000000..d6d7f487daea
--- /dev/null
+++ b/arch/loongarch/include/asm/qspinlock_paravirt.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_QSPINLOCK_PARAVIRT_H
+#define __ASM_QSPINLOCK_PARAVIRT_H
+
+void __lockfunc __pv_queued_spin_unlock_slowpath(struct qspinlock *lock, u8 locked);
+#endif
diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
index aee44610007d..758039eabdde 100644
--- a/arch/loongarch/kernel/paravirt.c
+++ b/arch/loongarch/kernel/paravirt.c
@@ -298,3 +298,91 @@ int __init pv_time_init(void)
return 0;
}
+
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+static bool native_vcpu_is_preempted(int cpu)
+{
+ return false;
+}
+
+/**
+ * queued_spin_unlock - release a queued spinlock
+ * @lock : Pointer to queued spinlock structure
+ */
+static void native_queued_spin_unlock(struct qspinlock *lock)
+{
+ /*
+ * unlock() needs release semantics:
+ */
+ smp_store_release(&lock->locked, 0);
+}
+
+static void paravirt_nop_kick(int cpu)
+{
+}
+
+static void paravirt_nop_wait(u8 *ptr, u8 val)
+{
+}
+
+static void kvm_wait(u8 *ptr, u8 val)
+{
+ if (READ_ONCE(*ptr) != val)
+ return;
+
+ __asm__ __volatile__("idle 0\n\t" : : : "memory");
+}
+
+/* Kick a cpu. Used to wake up a halted vcpu */
+static void kvm_kick_cpu(int cpu)
+{
+ kvm_hypercall1(KVM_HCALL_FUNC_KICK, cpu_logical_map(cpu));
+}
+
+bool pv_is_native_spin_unlock(void)
+{
+ return pv_lock_ops.queued_spin_unlock == native_queued_spin_unlock;
+}
+
+/*
+ * Setup pv_lock_ops for guest kernel.
+ */
+void __init kvm_spinlock_init(void)
+{
+ int feature;
+
+ /*
+ * pv_hash()/pv_unhas() need it whatever pv spinlock is
+ * enabled or not
+ */
+ __pv_init_lock_hash();
+
+ if (!kvm_para_available())
+ return;
+
+ /* Don't use the pvqspinlock code if there is only 1 vCPU. */
+ if (num_possible_cpus() == 1)
+ return;
+
+ feature = kvm_arch_para_features();
+ if (!(feature & KVM_FEATURE_PARAVIRT_SPINLOCK))
+ return;
+
+ if (nopvspin)
+ return;
+
+ pr_info("Using paravirt qspinlock\n");
+ pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
+ pv_lock_ops.queued_spin_unlock = __pv_queued_spin_unlock;
+ pv_lock_ops.wait = kvm_wait;
+ pv_lock_ops.kick = kvm_kick_cpu;
+}
+
+struct pv_lock_ops pv_lock_ops = {
+ .queued_spin_lock_slowpath = native_queued_spin_lock_slowpath,
+ .queued_spin_unlock = native_queued_spin_unlock,
+ .wait = paravirt_nop_wait,
+ .kick = paravirt_nop_kick,
+ .vcpu_is_preempted = native_vcpu_is_preempted,
+};
+#endif /* CONFIG_PARAVIRT_SPINLOCKS */
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index 1436d2465939..6bc0b182a2ce 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c
@@ -463,7 +463,7 @@ core_initcall(ipi_pm_init);
#endif
/* Preload SMP state for boot cpu */
-void smp_prepare_boot_cpu(void)
+void __init smp_prepare_boot_cpu(void)
{
unsigned int cpu, node, rr_node;
@@ -496,6 +496,8 @@ void smp_prepare_boot_cpu(void)
rr_node = next_node_in(rr_node, node_online_map);
}
}
+
+ kvm_spinlock_init();
}
/* called from main before smp_init() */
--
2.39.3Hi Bibo, kernel test robot noticed the following build warnings: [auto build test WARNING on 7846b618e0a4c3e08888099d1d4512722b39ca99] url: https://github.com/intel-lab-lkp/linux/commits/Bibo-Mao/LoongArch-KVM-Add-paravirt-qspinlock-in-kvm-side/20240723-160536 base: 7846b618e0a4c3e08888099d1d4512722b39ca99 patch link: https://lore.kernel.org/r/20240723073825.1811600-3-maobibo%40loongson.cn patch subject: [PATCH 2/2] LoongArch: KVM: Add paravirt qspinlock in guest side config: loongarch-kismet-CONFIG_PARAVIRT-CONFIG_PARAVIRT_SPINLOCKS-0-0 (https://download.01.org/0day-ci/archive/20240724/202407241016.NtaMVEAg-lkp@intel.com/config) reproduce: (https://download.01.org/0day-ci/archive/20240724/202407241016.NtaMVEAg-lkp@intel.com/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202407241016.NtaMVEAg-lkp@intel.com/ kismet warnings: (new ones prefixed by >>) >> kismet: WARNING: unmet direct dependencies detected for PARAVIRT when selected by PARAVIRT_SPINLOCKS -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
Hi Bibo,
kernel test robot noticed the following build errors:
[auto build test ERROR on 7846b618e0a4c3e08888099d1d4512722b39ca99]
url: https://github.com/intel-lab-lkp/linux/commits/Bibo-Mao/LoongArch-KVM-Add-paravirt-qspinlock-in-kvm-side/20240723-160536
base: 7846b618e0a4c3e08888099d1d4512722b39ca99
patch link: https://lore.kernel.org/r/20240723073825.1811600-3-maobibo%40loongson.cn
patch subject: [PATCH 2/2] LoongArch: KVM: Add paravirt qspinlock in guest side
config: loongarch-allmodconfig (https://download.01.org/0day-ci/archive/20240724/202407240320.qqd1uWiE-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 14.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240724/202407240320.qqd1uWiE-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202407240320.qqd1uWiE-lkp@intel.com/
All error/warnings (new ones prefixed by >>):
>> arch/loongarch/kernel/paravirt.c:309: warning: expecting prototype for queued_spin_unlock(). Prototype was for native_queued_spin_unlock() instead
--
In file included from include/linux/atomic.h:80,
from include/asm-generic/bitops/atomic.h:5,
from arch/loongarch/include/asm/bitops.h:27,
from include/linux/bitops.h:63,
from include/linux/kernel.h:23,
from include/linux/cpumask.h:11,
from include/linux/smp.h:13,
from kernel/locking/qspinlock.c:16:
kernel/locking/qspinlock_paravirt.h: In function 'pv_kick_node':
>> include/linux/atomic/atomic-arch-fallback.h:242:34: error: initialization of 'u8 *' {aka 'unsigned char *'} from incompatible pointer type 'enum vcpu_state *' [-Wincompatible-pointer-types]
242 | typeof(*(_ptr)) *___op = (_oldp), ___o = *___op, ___r; \
| ^
include/linux/atomic/atomic-instrumented.h:4908:9: note: in expansion of macro 'raw_try_cmpxchg_relaxed'
4908 | raw_try_cmpxchg_relaxed(__ai_ptr, __ai_oldp, __VA_ARGS__); \
| ^~~~~~~~~~~~~~~~~~~~~~~
kernel/locking/qspinlock_paravirt.h:377:14: note: in expansion of macro 'try_cmpxchg_relaxed'
377 | if (!try_cmpxchg_relaxed(&pn->state, &old, vcpu_hashed))
| ^~~~~~~~~~~~~~~~~~~
vim +309 arch/loongarch/kernel/paravirt.c
303
304 /**
305 * queued_spin_unlock - release a queued spinlock
306 * @lock : Pointer to queued spinlock structure
307 */
308 static void native_queued_spin_unlock(struct qspinlock *lock)
> 309 {
310 /*
311 * unlock() needs release semantics:
312 */
313 smp_store_release(&lock->locked, 0);
314 }
315
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On 2024/7/24 上午3:57, kernel test robot wrote:
> Hi Bibo,
>
> kernel test robot noticed the following build errors:
yes, forgot to mention, it depends on this patch
https://lore.kernel.org/lkml/20240721164552.50175-1-ubizjak@gmail.com/
Regards
Bibo Mao
>
> [auto build test ERROR on 7846b618e0a4c3e08888099d1d4512722b39ca99]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Bibo-Mao/LoongArch-KVM-Add-paravirt-qspinlock-in-kvm-side/20240723-160536
> base: 7846b618e0a4c3e08888099d1d4512722b39ca99
> patch link: https://lore.kernel.org/r/20240723073825.1811600-3-maobibo%40loongson.cn
> patch subject: [PATCH 2/2] LoongArch: KVM: Add paravirt qspinlock in guest side
> config: loongarch-allmodconfig (https://download.01.org/0day-ci/archive/20240724/202407240320.qqd1uWiE-lkp@intel.com/config)
> compiler: loongarch64-linux-gcc (GCC) 14.1.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240724/202407240320.qqd1uWiE-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202407240320.qqd1uWiE-lkp@intel.com/
>
> All error/warnings (new ones prefixed by >>):
>
>>> arch/loongarch/kernel/paravirt.c:309: warning: expecting prototype for queued_spin_unlock(). Prototype was for native_queued_spin_unlock() instead
> --
> In file included from include/linux/atomic.h:80,
> from include/asm-generic/bitops/atomic.h:5,
> from arch/loongarch/include/asm/bitops.h:27,
> from include/linux/bitops.h:63,
> from include/linux/kernel.h:23,
> from include/linux/cpumask.h:11,
> from include/linux/smp.h:13,
> from kernel/locking/qspinlock.c:16:
> kernel/locking/qspinlock_paravirt.h: In function 'pv_kick_node':
>>> include/linux/atomic/atomic-arch-fallback.h:242:34: error: initialization of 'u8 *' {aka 'unsigned char *'} from incompatible pointer type 'enum vcpu_state *' [-Wincompatible-pointer-types]
> 242 | typeof(*(_ptr)) *___op = (_oldp), ___o = *___op, ___r; \
> | ^
> include/linux/atomic/atomic-instrumented.h:4908:9: note: in expansion of macro 'raw_try_cmpxchg_relaxed'
> 4908 | raw_try_cmpxchg_relaxed(__ai_ptr, __ai_oldp, __VA_ARGS__); \
> | ^~~~~~~~~~~~~~~~~~~~~~~
> kernel/locking/qspinlock_paravirt.h:377:14: note: in expansion of macro 'try_cmpxchg_relaxed'
> 377 | if (!try_cmpxchg_relaxed(&pn->state, &old, vcpu_hashed))
> | ^~~~~~~~~~~~~~~~~~~
>
>
> vim +309 arch/loongarch/kernel/paravirt.c
>
> 303
> 304 /**
> 305 * queued_spin_unlock - release a queued spinlock
> 306 * @lock : Pointer to queued spinlock structure
> 307 */
> 308 static void native_queued_spin_unlock(struct qspinlock *lock)
> > 309 {
> 310 /*
> 311 * unlock() needs release semantics:
> 312 */
> 313 smp_store_release(&lock->locked, 0);
> 314 }
> 315
>
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