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[34.127.87.210]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39645b64c48sm1054146a91.8.2026.08.24.14.48.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2026 14:48:02 -0700 (PDT) Date: Mon, 24 Aug 2026 21:47:59 +0000 From: Samiullah Khawaja To: Pranjal Shrivastava Cc: iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Joerg Roedel , Suravee Suthikulpanit , Vasant Hegde , Ankit Soni , Jason Gunthorpe , Bjorn Helgaas , sashiko-bot@kernel.org Subject: Re: [PATCH v3 2/5] iommu/amd: Fix DTE clearing and rename iommu_ignore_device() Message-ID: References: <20260824122347.1588592-1-praan@google.com> <20260824122347.1588592-3-praan@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20260824122347.1588592-3-praan@google.com> On Mon, Aug 24, 2026 at 12:23:44PM +0000, Pranjal Shrivastava wrote: >The iommu_ignore_device() function currently uses memset() to manually >clear the primary Device Table Entry (DTE), which risks torn writes as >the hardware reads DTEs as atomic 256-bit qwords. Furthermore, clearing >the primary devid in the lookup table before calling setup_aliases() >causes rlookup_amd_iommu() to fail for aliases. This prevents clearing >the DTEs for DMA aliases. > >Fix this by replacing the manual memset with a dedicated helper that >invalidates the DTE by clearing the lower 128 bits (having the Valid bit) >first, followed by the upper 128 bits. The cleared state is then >explicitly cloned to all aliases before the lookup tables are nullified. > >Rename the function to iommu_disable_device() more accurately >reflects its intent, as we still support IRQ remapping for these devices) > >Fixes: 99fc4ac3d297 ("iommu/amd: Introduce per PCI segment alias_table") >Reported-by: sashiko-bot@kernel.org >Closes: https://lore.kernel.org/all/20260529153216.2AD1E1F00899@smtp.kernel.org/ >Suggested-by: Jason Gunthorpe >Signed-off-by: Pranjal Shrivastava >--- > drivers/iommu/amd/iommu.c | 53 ++++++++++++++++++++++++++------------- > 1 file changed, 36 insertions(+), 17 deletions(-) > Reviewed-by: Samiullah Khawaja