linux-kernel - [RFC PATCH 13/16] KVM: arm64: Stash "mmu_seq" in "struct kvm_page

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Message-ID: <20250821210042.3451147-14-seanjc@google.com>
Date: Thu, 21 Aug 2025 14:00:39 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Sean Christopherson <seanjc@...gle.com>, 
	James Houghton <jthoughton@...gle.com>
Subject: [RFC PATCH 13/16] KVM: arm64: Stash "mmu_seq" in "struct kvm_page_fault"

Track the MMU notifier sequence count snapshot in "struct kvm_page_fault"
in anticipation of moving the mmap_lock-protected code to a separate
helper.  Attaching mmu_seq to the fault could also prove useful in the
future, e.g. for additional refactorings.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/arm64/include/asm/kvm_host.h | 1 +
 arch/arm64/kvm/mmu.c              | 5 ++---
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 4d131be08d8d..6a99f7fa065d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -430,6 +430,7 @@ struct kvm_page_fault {
 	unsigned long hva;
 	kvm_pfn_t pfn;
 	struct page *page;
+	unsigned long mmu_seq;
 
 	struct {
 		vm_flags_t vm_flags;
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index aa6ee72bef51..575a4f9f2583 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1471,7 +1471,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	int ret = 0;
 	bool writable, force_pte = false;
 	bool s2_force_noncacheable = false;
-	unsigned long mmu_seq;
 	struct kvm *kvm = vcpu->kvm;
 	struct vm_area_struct *vma;
 	void *memcache;
@@ -1612,7 +1611,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	 * Rely on mmap_read_unlock() for an implicit smp_rmb(), which pairs
 	 * with the smp_wmb() in kvm_mmu_invalidate_end().
 	 */
-	mmu_seq = vcpu->kvm->mmu_invalidate_seq;
+	fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq;
 	mmap_read_unlock(current->mm);
 
 	fault->pfn = __kvm_faultin_pfn(fault->slot, fault->gfn,
@@ -1691,7 +1690,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 
 	kvm_fault_lock(kvm);
 	pgt = vcpu->arch.hw_mmu->pgt;
-	if (mmu_invalidate_retry(kvm, mmu_seq)) {
+	if (mmu_invalidate_retry(kvm, fault->mmu_seq)) {
 		ret = -EAGAIN;
 		goto out_unlock;
 	}
-- 
2.51.0.261.g7ce5a0a67e-goog