Commit 8cc9dc1a authored by Ankit Agrawal's avatar Ankit Agrawal Committed by Oliver Upton
Browse files

KVM: arm64: Rename the device variable to s2_force_noncacheable 



To perform cache maintenance on a region of memory, KVM/arm64 relies on
that region having a cacheable alias in the kernel's address space which
can be used with CMO instructions.

The 'device' variable is somewhat of a misnomer, as it actually
indicates whether or not the stage-2 alias is allowed to have cacheable
memory attributes. The resulting stage-2 memory attributes are further
modified by VM_ALLOW_ANY_UNCACHED, selecting between Normal-NC or
Device-nGnRE depending on what the endpoint supports.

Rename the to s2_force_noncacheable such that its purpose is a bit more
obvious.

CC: Catalin Marinas <catalin.marinas@arm.com>
Suggested-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Tested-by: default avatarDonald Dutile <ddutile@redhat.com>
Signed-off-by: default avatarAnkit Agrawal <ankita@nvidia.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20250705071717.5062-2-ankita@nvidia.com


[ Oliver: addressed typos, wound up rewriting changelog ]
Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 86731a2a

arch/arm64/kvm/mmu.c

+6 −6
Original line number Diff line number Diff line
@@ -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