linux-kernel - [RFC PATCH 13/24] KVM: nSVM: Parameterize svm_flush_tlb_asid() by is_guest

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Message-ID: <20250326193619.3714986-14-yosry.ahmed@linux.dev>
Date: Wed, 26 Mar 2025 19:36:08 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
	Jim Mattson <jmattson@...gle.com>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Rik van Riel <riel@...riel.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	x86@...nel.org,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [RFC PATCH 13/24] KVM: nSVM: Parameterize svm_flush_tlb_asid() by is_guest_mode

svm_flush_tlb_asid() currently operates on the current VMCB. In
preparation for properly tracking TLB flushes for L1 and L2 ASIDs,
refactor it to take is_guest_mode and find the proper VMCB. All existing
callers pass is_guest_mode(vcpu) to maintain existing behavior for now.

Move the comment about only flushing the current ASID to
svm_flush_tlb_all(), where it probably should have been anyway, because
svm_flush_tlb_asid() now flushes a given ASID, not the current ASID.

Create a svm_flush_tlb_guest() wrapper to use as the flush_tlb_guest()
callback.

No functional change intended.

Signed-off-by: Yosry Ahmed <yosry.ahmed@...ux.dev>
---
 arch/x86/kvm/svm/svm.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 865c5ce4fa473..fb6b9f88a1504 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4016,25 +4016,24 @@ static void svm_enable_nmi_window(struct kvm_vcpu *vcpu)
 	svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
 }
 
-static void svm_flush_tlb_asid(struct kvm_vcpu *vcpu)
+static struct vmcb *svm_get_vmcb(struct vcpu_svm *svm, bool is_guest_mode)
+{
+	return is_guest_mode ? svm->nested.vmcb02.ptr : svm->vmcb01.ptr;
+}
+
+static void svm_flush_tlb_asid(struct kvm_vcpu *vcpu, bool is_guest_mode)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
+	struct vmcb *vmcb = svm_get_vmcb(svm, is_guest_mode);
 
 	/*
 	 * Unlike VMX, SVM doesn't provide a way to flush only NPT TLB entries.
 	 * A TLB flush for the current ASID flushes both "host" and "guest" TLB
 	 * entries, and thus is a superset of Hyper-V's fine grained flushing.
 	 */
-	kvm_hv_vcpu_purge_flush_tlb(vcpu, is_guest_mode(vcpu));
-
-	/*
-	 * Flush only the current ASID even if the TLB flush was invoked via
-	 * kvm_flush_remote_tlbs().  Although flushing remote TLBs requires all
-	 * ASIDs to be flushed, KVM uses a single ASID for L1 and L2, and
-	 * unconditionally does a TLB flush on both nested VM-Enter and nested
-	 * VM-Exit (via kvm_mmu_reset_context()).
-	 */
-	vmcb_set_flush_asid(svm->vmcb);
+	kvm_hv_vcpu_purge_flush_tlb(vcpu, is_guest_mode);
+	if (vmcb)
+		vmcb_set_flush_asid(vmcb);
 }
 
 static void svm_flush_tlb_current(struct kvm_vcpu *vcpu)
@@ -4050,7 +4049,7 @@ static void svm_flush_tlb_current(struct kvm_vcpu *vcpu)
 	if (svm_hv_is_enlightened_tlb_enabled(vcpu) && VALID_PAGE(root_tdp))
 		hyperv_flush_guest_mapping(root_tdp);
 
-	svm_flush_tlb_asid(vcpu);
+	svm_flush_tlb_asid(vcpu, is_guest_mode(vcpu));
 }
 
 static void svm_flush_tlb_all(struct kvm_vcpu *vcpu)
@@ -4065,7 +4064,14 @@ static void svm_flush_tlb_all(struct kvm_vcpu *vcpu)
 	if (WARN_ON_ONCE(svm_hv_is_enlightened_tlb_enabled(vcpu)))
 		hv_flush_remote_tlbs(vcpu->kvm);
 
-	svm_flush_tlb_asid(vcpu);
+	/*
+	 * Flush only the current ASID even if the TLB flush was invoked via
+	 * kvm_flush_remote_tlbs().  Although flushing remote TLBs requires all
+	 * ASIDs to be flushed, KVM uses a single ASID for L1 and L2, and
+	 * unconditionally does a TLB flush on both nested VM-Enter and nested
+	 * VM-Exit (via kvm_mmu_reset_context()).
+	 */
+	svm_flush_tlb_asid(vcpu, is_guest_mode(vcpu));
 }
 
 static void svm_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t gva)
@@ -4075,6 +4081,11 @@ static void svm_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t gva)
 	invlpga(gva, svm_get_current_asid(svm));
 }
 
+static void svm_flush_tlb_guest(struct kvm_vcpu *vcpu)
+{
+	svm_flush_tlb_asid(vcpu, is_guest_mode(vcpu));
+}
+
 static inline void sync_cr8_to_lapic(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -5187,7 +5198,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 	.flush_tlb_all = svm_flush_tlb_all,
 	.flush_tlb_current = svm_flush_tlb_current,
 	.flush_tlb_gva = svm_flush_tlb_gva,
-	.flush_tlb_guest = svm_flush_tlb_asid,
+	.flush_tlb_guest = svm_flush_tlb_guest,
 
 	.vcpu_pre_run = svm_vcpu_pre_run,
 	.vcpu_run = svm_vcpu_run,
-- 
2.49.0.395.g12beb8f557-goog