From 01b4f510b9f467abfc781e198e810e1ecffb782e Mon Sep 17 00:00:00 2001
From: Oliver Upton <oupton@google.com>
Date: Tue, 27 Oct 2020 16:10:42 -0700
Subject: [PATCH] kvm: x86: ensure pv_cpuid.features is initialized when
enabling cap
Make the paravirtual cpuid enforcement mechanism idempotent to ioctl()
ordering by updating pv_cpuid.features whenever userspace requests the
capability. Extract this update out of kvm_update_cpuid_runtime() into a
new helper function and move its other call site into
kvm_vcpu_after_set_cpuid() where it more likely belongs.
Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
Signed-off-by: Oliver Upton <oupton@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Message-Id: <20201027231044.655110-5-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/cpuid.c | 23 ++++++++++++++++-------
arch/x86/kvm/cpuid.h | 1 +
arch/x86/kvm/x86.c | 2 ++
3 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 06a278b3701d12..d50041f570e890 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -90,6 +90,20 @@ static int kvm_check_cpuid(struct kvm_cpuid_entry2 *entries, int nent)
return 0;
}
+void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
+{
+ struct kvm_cpuid_entry2 *best;
+
+ best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
+
+ /*
+ * save the feature bitmap to avoid cpuid lookup for every PV
+ * operation
+ */
+ if (best)
+ vcpu->arch.pv_cpuid.features = best->eax;
+}
+
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
@@ -124,13 +138,6 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
- /*
- * save the feature bitmap to avoid cpuid lookup for every PV
- * operation
- */
- if (best)
- vcpu->arch.pv_cpuid.features = best->eax;
-
if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {
best = kvm_find_cpuid_entry(vcpu, 0x1, 0);
if (best)
@@ -162,6 +169,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
vcpu->arch.guest_supported_xcr0 =
(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
+ kvm_update_pv_runtime(vcpu);
+
vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
kvm_mmu_reset_context(vcpu);
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index bf8577947ed23f..f7a6e8f83783cd 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -11,6 +11,7 @@ extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
void kvm_set_cpu_caps(void);
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu);
+void kvm_update_pv_runtime(struct kvm_vcpu *vcpu);
struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
u32 function, u32 index);
int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d12820acc54813..948561183fd1fd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4611,6 +4611,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
vcpu->arch.pv_cpuid.enforce = cap->args[0];
+ if (vcpu->arch.pv_cpuid.enforce)
+ kvm_update_pv_runtime(vcpu);
return 0;
--
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