linux-kernel - [PATCH v5 25/44] KVM: x86: Use KVM_REQ_RECALC

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Message-ID: <20250806195706.1650976-26-seanjc@google.com>
Date: Wed,  6 Aug 2025 12:56:47 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Xin Li <xin@...or.com>, "H. Peter Anvin" <hpa@...or.com>, 
	Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, loongarch@...ts.linux.dev, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, Kan Liang <kan.liang@...ux.intel.com>, 
	Yongwei Ma <yongwei.ma@...el.com>, Mingwei Zhang <mizhang@...gle.com>, 
	Xiong Zhang <xiong.y.zhang@...ux.intel.com>, Sandipan Das <sandipan.das@....com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [PATCH v5 25/44] KVM: x86: Use KVM_REQ_RECALC_INTERCEPTS to react to
 CPUID updates

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@...gle.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