[PATCH v5 25/44] KVM: x86: Use KVM_REQ_RECALC_INTERCEPTS to react to CPUID updates

Sean Christopherson
2025-08-06T19:58:15Z

Defer recalculating MSR and instruction intercepts after a CPUID update
via RECALC_INTERCEPTS to converge on RECALC_INTERCEPTS as the "official"
mechanism for triggering recalcs. As a bonus, because KVM does a "recalc"
during vCPU creation, and every functional VMM sets CPUID at least once,
for all intents and purposes this saves at least one recalc.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/cpuid.c | 2 ++
arch/x86/kvm/svm/svm.c | 4 +---
arch/x86/kvm/vmx/vmx.c | 3 ---
3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e2836a255b16..cc16e28bfab2 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -448,6 +448,8 @@ void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
* adjustments to the reserved GPA bits.
*/
kvm_mmu_after_set_cpuid(vcpu);
+
+ kvm_make_request(KVM_REQ_RECALC_INTERCEPTS, vcpu);
}

int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 3d9dcc66a407..ef7dffc54dca 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1225,7 +1225,7 @@ static void init_vmcb(struct kvm_vcpu *vcpu)

svm_hv_init_vmcb(vmcb);

- svm_recalc_intercepts(vcpu);
+ kvm_make_request(KVM_REQ_RECALC_INTERCEPTS, vcpu);

vmcb_mark_all_dirty(vmcb);

@@ -4478,8 +4478,6 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)

if (sev_guest(vcpu->kvm))
sev_vcpu_after_set_cpuid(svm);
-
- svm_recalc_intercepts(vcpu);
}

static bool svm_has_wbinvd_exit(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2244ca074e9d..6094de4855d6 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7782,9 +7782,6 @@ void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
vmx->msr_ia32_feature_control_valid_bits &=
~FEAT_CTL_SGX_LC_ENABLED;

- /* Recalc MSR interception to account for feature changes. */
- vmx_recalc_intercepts(vcpu);
-
/* Refresh #PF interception to account for MAXPHYADDR changes. */
vmx_update_exception_bitmap(vcpu);
}
--
2.50.1.565.gc32cd1483b-goog