linux-kernel - [PATCH v8 1/6] KVM: arm64: Rename the device variable to s2_force

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Message-ID: <20250620120946.2991-2-ankita@nvidia.com>
Date: Fri, 20 Jun 2025 12:09:41 +0000
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Subject: [PATCH v8 1/6] KVM: arm64: Rename the device variable to s2_force_noncacheable

From: Ankit Agrawal <ankita@...dia.com>

For cache maintenance on a region, ARM KVM relies on that
region to be mapped to the Kernal virtual address as CMOs
operate on VA.

Currently the device variable is effectively trying to setup
the S2 mapping as non cacheable for memory regions that are
not mapped in the Kernel VA. This could be either device or
Normal_NC depending on the VM_ALLOW_ANY_UNCACHED flag in the
VMA.

Thus "device" could be better renamed to s2_force_noncacheable
which implies that it is ensuring that region be mapped as
non-cacheable.

CC: Catalin Marinas <catalin.marinas@....com>
Suggested-by: Jason Gunthorpe <jgg@...dia.com>
Signed-off-by: Ankit Agrawal <ankita@...dia.com>
---
 arch/arm64/kvm/mmu.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 2942ec92c5a4..1601ab9527d4 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1478,7 +1478,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	int ret = 0;
 	bool write_fault, writable, force_pte = false;
 	bool exec_fault, mte_allowed;
-	bool device = false, vfio_allow_any_uc = false;
+	bool s2_force_noncacheable = false, vfio_allow_any_uc = false;
 	unsigned long mmu_seq;
 	phys_addr_t ipa = fault_ipa;
 	struct kvm *kvm = vcpu->kvm;
@@ -1653,7 +1653,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		 * In both cases, we don't let transparent_hugepage_adjust()
 		 * change things at the last minute.
 		 */
-		device = true;
+		s2_force_noncacheable = true;
 	} else if (logging_active && !write_fault) {
 		/*
 		 * Only actually map the page as writable if this was a write
@@ -1662,7 +1662,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		writable = false;
 	}
 
-	if (exec_fault && device)
+	if (exec_fault && s2_force_noncacheable)
 		return -ENOEXEC;
 
 	/*
@@ -1695,7 +1695,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	 * If we are not forced to use page mapping, check if we are
 	 * backed by a THP and thus use block mapping if possible.
 	 */
-	if (vma_pagesize == PAGE_SIZE && !(force_pte || device)) {
+	if (vma_pagesize == PAGE_SIZE && !(force_pte || s2_force_noncacheable)) {
 		if (fault_is_perm && fault_granule > PAGE_SIZE)
 			vma_pagesize = fault_granule;
 		else
@@ -1709,7 +1709,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 		}
 	}
 
-	if (!fault_is_perm && !device && kvm_has_mte(kvm)) {
+	if (!fault_is_perm && !s2_force_noncacheable && kvm_has_mte(kvm)) {
 		/* Check the VMM hasn't introduced a new disallowed VMA */
 		if (mte_allowed) {
 			sanitise_mte_tags(kvm, pfn, vma_pagesize);
@@ -1725,7 +1725,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	if (exec_fault)
 		prot |= KVM_PGTABLE_PROT_X;
 
-	if (device) {
+	if (s2_force_noncacheable) {
 		if (vfio_allow_any_uc)
 			prot |= KVM_PGTABLE_PROT_NORMAL_NC;
 		else
-- 
2.34.1