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Sat, 20 Dec 2025 17:43:16 -0800 (PST) Received: from localhost.localdomain ([2a02:a31b:20c3:6680:4cc9:1698:dce5:4976]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-64b91494cd7sm6035057a12.16.2025.12.20.17.43.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 20 Dec 2025 17:43:15 -0800 (PST) From: Dmytro Maluka To: David Woodhouse , Lu Baolu , iommu@lists.linux.dev Cc: Joerg Roedel , Will Deacon , Robin Murphy , linux-kernel@vger.kernel.org, "Vineeth Pillai (Google)" , Aashish Sharma , Grzegorz Jaszczyk , Chuanxiao Dong , Kevin Tian , Dmytro Maluka Subject: [PATCH 2/2] iommu/vt-d: Use WRITE_ONCE for setting root table entries Date: Sun, 21 Dec 2025 02:43:02 +0100 Message-ID: <20251221014302.17738-3-dmaluka@chromium.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251221014302.17738-1-dmaluka@chromium.org> References: <20251221014302.17738-1-dmaluka@chromium.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Like context table entries in the previous patch, root table entries may also be set up at runtime, when DMA translation is already enabled (e.g. due to a device hotplug). So to stay on the safe side, use WRITE_ONCE when setting a root table entry, to prevent the compiler from doing store tearing which could result in setting the present bit earlier than the context table address bits. Signed-off-by: Dmytro Maluka --- drivers/iommu/intel/iommu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 134302fbcd92..fe4d0d210a5f 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -374,7 +374,7 @@ struct context_entry *iommu_context_addr(struct intel_i= ommu *iommu, u8 bus, =20 __iommu_flush_cache(iommu, (void *)context, CONTEXT_SIZE); phy_addr =3D virt_to_phys((void *)context); - *entry =3D phy_addr | 1; + WRITE_ONCE(*entry, phy_addr | 1); __iommu_flush_cache(iommu, entry, sizeof(*entry)); } return &context[devfn]; --=20 2.47.3