[PATCH v2 5/5] KVM: X86: Expose PREEMT_COUNT CPUID feature bit to guest

Wanpeng Li
2022-04-01T08:11:59Z

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 <wanpengli@tencent.com>
---
Documentation/virt/kvm/cpuid.rst | 3 +++
arch/x86/kvm/cpuid.c | 3 ++-
2 files changed, 5 insertions(+), 1 deletion(-)

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 a00cd97b2623..c514c0419593 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1072,7 +1072,8 @@ 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);
--
2.25.1