linux-kernel - [RFC PATCH 11/16] KVM: arm64: Drop local mte_allowed, use vm

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Message-ID: <20250821210042.3451147-12-seanjc@google.com>
Date: Thu, 21 Aug 2025 14:00:37 -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 11/16] KVM: arm64: Drop local mte_allowed, use vm_flags snapshot

Drop user_mem_abort()'s local mte_allowed and instead use the vm_flags
snapshot.  The redundant variables aren't problematic per se, but will be
quite awkward when a future change moves the vm_flags snapshot into
"struct kvm_page_fault".

Opportunistically drop kvm_vma_mte_allowed() and open code the vm_flags
check in the memslot preparation code, as there's little value in hiding
VM_MTE_ALLOWED (arguably negative "value), and the fault path can't use
the VMA-based helper (because looking at the VMA outside of mmap_lock is
unsafe).

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/arm64/kvm/mmu.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index e1375296940b..b85968019dd4 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1454,11 +1454,6 @@ static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
 	}
 }
 
-static bool kvm_vma_mte_allowed(struct vm_area_struct *vma)
-{
-	return vma->vm_flags & VM_MTE_ALLOWED;
-}
-
 static bool kvm_vma_is_cacheable(struct vm_area_struct *vma)
 {
 	switch (FIELD_GET(PTE_ATTRINDX_MASK, pgprot_val(vma->vm_page_prot))) {
@@ -1475,7 +1470,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 {
 	int ret = 0;
 	bool writable, force_pte = false;
-	bool mte_allowed, is_vma_cacheable;
+	bool is_vma_cacheable;
 	bool s2_force_noncacheable = false;
 	unsigned long mmu_seq;
 	struct kvm *kvm = vcpu->kvm;
@@ -1606,7 +1601,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	}
 
 	fault->gfn = fault->ipa >> PAGE_SHIFT;
-	mte_allowed = kvm_vma_mte_allowed(vma);
 
 	vm_flags = vma->vm_flags;
 
@@ -1724,7 +1718,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 
 	if (!fault->is_perm && !s2_force_noncacheable && kvm_has_mte(kvm)) {
 		/* Check the VMM hasn't introduced a new disallowed VMA */
-		if (mte_allowed) {
+		if (vm_flags & VM_MTE_ALLOWED) {
 			sanitise_mte_tags(kvm, fault->pfn, vma_pagesize);
 		} else {
 			ret = -EFAULT;
@@ -2215,7 +2209,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 		if (!vma)
 			break;
 
-		if (kvm_has_mte(kvm) && !kvm_vma_mte_allowed(vma)) {
+		if (kvm_has_mte(kvm) && !(vma->vm_flags & VM_MTE_ALLOWED)) {
 			ret = -EINVAL;
 			break;
 		}
-- 
2.51.0.261.g7ce5a0a67e-goog