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From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
To: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev
Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>,
	Steven Price <steven.price@arm.com>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Joey Gouly <joey.gouly@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	"Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
Subject: [PATCH 3/4] arm64: mte: update code comments
Date: Mon, 28 Oct 2024 15:10:13 +0530	[thread overview]
Message-ID: <20241028094014.2596619-4-aneesh.kumar@kernel.org> (raw)
In-Reply-To: <20241028094014.2596619-1-aneesh.kumar@kernel.org>

commit d77e59a8fccd ("arm64: mte: Lock a page for MTE tag
initialisation") updated the locking such the kernel now allows
VM_SHARED mapping with MTE. Update the code comment to reflect this.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 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 a509b63bd4dd..b5824e93cee0 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1390,11 +1390,8 @@ static int get_vma_page_shift(struct vm_area_struct *vma, unsigned long hva)
  * able to see the page's tags and therefore they must be initialised first. If
  * PG_mte_tagged is set, tags have already been initialised.
  *
- * The race in the test/set of the PG_mte_tagged flag is handled by:
- * - preventing VM_SHARED mappings in a memslot with MTE preventing two VMs
- *   racing to santise the same page
- * - mmap_lock protects between a VM faulting a page in and the VMM performing
- *   an mprotect() to add VM_MTE
+ * The race in the test/set of the PG_mte_tagged flag is handled by
+ * using PG_mte_lock and PG_mte_tagged together.
  */
 static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
 			      unsigned long size)
@@ -1646,7 +1643,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 	}
 
 	if (!fault_is_perm && !device && kvm_has_mte(kvm)) {
-		/* Check the VMM hasn't introduced a new disallowed VMA */
+		/*
+		 *  not a permission fault implies a translation fault which
+		 *  means mapping the page for the first time
+		 */
 		if (mte_allowed) {
 			sanitise_mte_tags(kvm, pfn, vma_pagesize);
 		} else {
-- 
2.43.0


  parent reply	other threads:[~2024-10-28  9:40 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-28  9:40 [PATCH 0/4] Add support for NoTagAccess memory attribute Aneesh Kumar K.V (Arm)
2024-10-28  9:40 ` [PATCH 1/4] arm64: Update the values to binary from hex Aneesh Kumar K.V (Arm)
2024-10-28  9:40 ` [PATCH 2/4] arm64: cpufeature: add Allocation Tag Access Permission (MTE_PERM) feature Aneesh Kumar K.V (Arm)
2024-10-28  9:40 ` Aneesh Kumar K.V (Arm) [this message]
2024-10-28 10:33   ` [PATCH 3/4] arm64: mte: update code comments Marc Zyngier
2024-10-28 12:47     ` Aneesh Kumar K.V
2024-10-28 18:09       ` Marc Zyngier
2024-10-28  9:40 ` [PATCH 4/4] arm64: mte: Use stage-2 NoTagAccess memory attribute if supported Aneesh Kumar K.V (Arm)
2024-10-28 10:54   ` Marc Zyngier
2024-10-28 13:28     ` Aneesh Kumar K.V
2024-10-28 18:37       ` Marc Zyngier
2024-11-08  7:59         ` Aneesh Kumar K.V
2024-11-12 11:51           ` Marc Zyngier
2024-11-15 16:23             ` Catalin Marinas
2024-10-28 14:44   ` Oliver Upton
2024-10-28 14:52     ` Aneesh Kumar K.V
2024-10-28 15:07       ` Oliver Upton

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