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From: Peter Collingbourne <pcc@google.com>
To: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
Cc: Peter Collingbourne <pcc@google.com>,
	Cornelia Huck <cohuck@redhat.com>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,
	 Evgenii Stepanov <eugenis@google.com>,
	kvm@vger.kernel.org,  Steven Price <steven.price@arm.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: [PATCH v4 6/8] KVM: arm64: unify the tests for VMAs in memslots when MTE is enabled
Date: Tue, 20 Sep 2022 20:51:38 -0700	[thread overview]
Message-ID: <20220921035140.57513-7-pcc@google.com> (raw)
In-Reply-To: <20220921035140.57513-1-pcc@google.com>

Previously we allowed creating a memslot containing a private mapping that
was not VM_MTE_ALLOWED, but would later reject KVM_RUN with -EFAULT. Now
we reject the memory region at memslot creation time.

Since this is a minor tweak to the ABI (a VMM that created one of
these memslots would fail later anyway), no VMM to my knowledge has
MTE support yet, and the hardware with the necessary features is not
generally available, we can probably make this ABI change at this point.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
---
 arch/arm64/kvm/mmu.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index bebfd1e0bbf0..e34fbabd8b93 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1073,6 +1073,19 @@ static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
 	}
 }
 
+static bool kvm_vma_mte_allowed(struct vm_area_struct *vma)
+{
+	/*
+	 * VM_SHARED mappings are not allowed with MTE to avoid races
+	 * when updating the PG_mte_tagged page flag, see
+	 * sanitise_mte_tags for more details.
+	 */
+	if (vma->vm_flags & VM_SHARED)
+		return false;
+
+	return vma->vm_flags & VM_MTE_ALLOWED;
+}
+
 static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			  struct kvm_memory_slot *memslot, unsigned long hva,
 			  unsigned long fault_status)
@@ -1249,9 +1262,8 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	}
 
 	if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
-		/* Check the VMM hasn't introduced a new VM_SHARED VMA */
-		if ((vma->vm_flags & VM_MTE_ALLOWED) &&
-		    !(vma->vm_flags & VM_SHARED)) {
+		/* Check the VMM hasn't introduced a new disallowed VMA */
+		if (kvm_vma_mte_allowed(vma)) {
 			sanitise_mte_tags(kvm, pfn, vma_pagesize);
 		} else {
 			ret = -EFAULT;
@@ -1695,12 +1707,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 		if (!vma)
 			break;
 
-		/*
-		 * VM_SHARED mappings are not allowed with MTE to avoid races
-		 * when updating the PG_mte_tagged page flag, see
-		 * sanitise_mte_tags for more details.
-		 */
-		if (kvm_has_mte(kvm) && vma->vm_flags & VM_SHARED) {
+		if (kvm_has_mte(kvm) && !kvm_vma_mte_allowed(vma)) {
 			ret = -EINVAL;
 			break;
 		}
-- 
2.37.3.968.ga6b4b080e4-goog


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  parent reply	other threads:[~2022-09-21  3:55 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-21  3:51 [PATCH v4 0/8] KVM: arm64: permit MAP_SHARED mappings with MTE enabled Peter Collingbourne
2022-09-21  3:51 ` [PATCH v4 1/8] mm: Do not enable PG_arch_2 for all 64-bit architectures Peter Collingbourne
2022-09-21  9:17   ` Steven Price
2022-09-21  3:51 ` [PATCH v4 2/8] arm64: mte: Fix/clarify the PG_mte_tagged semantics Peter Collingbourne
2022-09-21  3:51 ` [PATCH v4 3/8] KVM: arm64: Simplify the sanitise_mte_tags() logic Peter Collingbourne
2022-09-21  3:51 ` [PATCH v4 4/8] mm: Add PG_arch_3 page flag Peter Collingbourne
2022-09-21  9:17   ` Steven Price
2022-09-21  3:51 ` [PATCH v4 5/8] arm64: mte: Lock a page for MTE tag initialisation Peter Collingbourne
2022-09-21  3:51 ` Peter Collingbourne [this message]
2022-09-21  3:51 ` [PATCH v4 7/8] KVM: arm64: permit all VM_MTE_ALLOWED mappings with MTE enabled Peter Collingbourne
2022-09-21  3:51 ` [PATCH v4 8/8] Documentation: document the ABI changes for KVM_CAP_ARM_MTE Peter Collingbourne

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