[PATCH 05/11] KVM: SVM: Use the active VMCB's MSR bitmap when checking if MSR is intercepted

[Paolo Bonzini]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

Use the MSR permission bitmap of the active VMCB instead of assuming that
KVM is always using vmcb02's bitmap when L2 is active, as KVM uses msrpm02
if and only if L1 wants to intercept MSR accesses, i.e. if and only if KVM
needs to merge msprm01 with msrpm12.

Don't bother tracking the virtual address of the bitmap that's being used,
as __va() is cheap on x86, and caching the virtual address would introduce
yet another source of potentially stale information.

Fixes: b2ac58f90540 ("KVM/SVM: Allow direct access to MSR_IA32_SPEC_CTRL")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Stefan Teodorescu <fane@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-ID: <20260826195833.844526-1-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/svm/svm.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f4f488328ea4..1f279cd91ecf 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -673,16 +673,7 @@ static void clr_dr_intercepts(struct vcpu_svm *svm)
 
 static bool msr_write_intercepted(struct vcpu_svm *svm, u32 msr)
 {
-	/*
-	 * For non-nested case:
-	 * If the L01 MSR bitmap does not intercept the MSR, then we need to
-	 * save it.
-	 *
-	 * For nested case:
-	 * If the L02 MSR bitmap does not intercept the MSR, then we need to
-	 * save it.
-	 */
-	void *msrpm = is_guest_mode(&svm->vcpu) ? svm->nested.msrpm : svm->msrpm;
+	void *msrpm = __va(svm->vmcb->control.msrpm_base_pa);
 
 	return svm_test_msr_bitmap_write(msrpm, msr);
 }
-- 
2.52.0