[5/5] KVM: X86: Expose PREEMT_COUNT CPUID feature bit to guest

Commit Message

Wanpeng Li March 11, 2022, 8:29 a.m. UTC

From: Wanpeng Li <[e-mail]>

Expose the PREEMPT_COUNT feature bit to the guest, the guest can check this
feature bit before using MSR_KVM_PREEMPT_COUNT.

Signed-off-by: Wanpeng Li <[e-mail]>
---
 Documentation/virt/kvm/cpuid.rst | 3 +++
 arch/x86/kvm/cpuid.c             | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

Patch

diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
index bda3e3e737d7..c45158af98a7 100644
--- a/Documentation/virt/kvm/cpuid.rst
+++ b/Documentation/virt/kvm/cpuid.rst
@@ -103,6 +103,9 @@  KVM_FEATURE_HC_MAP_GPA_RANGE       16          guest checks this feature bit bef
 KVM_FEATURE_MIGRATION_CONTROL      17          guest checks this feature bit before
                                                using MSR_KVM_MIGRATION_CONTROL
 
+KVM_FEATURE_PREEMPT_COUNT          18          guest checks this feature bit before
+                                               using MSR_KVM_PREEMPT_COUNT
+
 KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24          host will warn if no guest-side
                                                per-cpu warps are expected in
                                                kvmclock
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 58b0b4e0263c..4785f5a63d8d 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1071,7 +1071,8 @@  static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 			     (1 << KVM_FEATURE_PV_SEND_IPI) |
 			     (1 << KVM_FEATURE_POLL_CONTROL) |
 			     (1 << KVM_FEATURE_PV_SCHED_YIELD) |
-			     (1 << KVM_FEATURE_ASYNC_PF_INT);
+			     (1 << KVM_FEATURE_ASYNC_PF_INT) |
+			     (1 << KVM_FEATURE_PREEMPT_COUNT);
 
 		if (sched_info_on())
 			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);