linux-kernel - [PATCH 5/7] KVM: SVM: Flush the ASID when running on a new CPU

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Message-ID: <20250313215540.4171762-6-yosry.ahmed@linux.dev>
Date: Thu, 13 Mar 2025 21:55:38 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	x86@...nel.org,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH 5/7] KVM: SVM: Flush the ASID when running on a new CPU

Currently, when a vCPU is migrated to a new physical CPU, the ASID
generation is reset to trigger allocating a new ASID. In preparation for
using a static ASID per VM, just flush the ASID in this case (falling
back to flushing everything if FLUSBYASID is not available).

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
 arch/x86/kvm/svm/svm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e5064fbefb822..b8a3fc81fc9c8 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3626,12 +3626,12 @@ static int pre_svm_run(struct kvm_vcpu *vcpu)
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 	/*
-	 * If the previous vmrun of the vmcb occurred on a different physical
-	 * cpu, then mark the vmcb dirty and assign a new asid.  Hardware's
-	 * vmcb clean bits are per logical CPU, as are KVM's asid assignments.
+	 * If the previous VMRUN of the VMCB occurred on a different physical
+	 * CPU, then mark the VMCB dirty and flush the ASID.  Hardware's
+	 * VMCB clean bits are per logical CPU, as are KVM's ASID assignments.
 	 */
 	if (unlikely(svm->current_vmcb->cpu != vcpu->cpu)) {
-		svm->current_vmcb->asid_generation = 0;
+		svm_vmcb_set_flush_asid(svm->vmcb);
 		vmcb_mark_all_dirty(svm->vmcb);
 		svm->current_vmcb->cpu = vcpu->cpu;
         }
-- 
2.49.0.rc1.451.g8f38331e32-goog