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[34.124.129.10]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2cad7894b20sm9826605ad.78.2026.07.03.06.46.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jul 2026 06:46:10 -0700 (PDT) Date: Fri, 3 Jul 2026 13:46:04 +0000 From: Pranjal Shrivastava To: iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Will Deacon , Joerg Roedel Cc: Joerg Roedel , Will Deacon , Robin Murphy , Baolu Lu , Jason Gunthorpe , Kevin Tian , Bjorn Helgaas , Samiullah Khawaja Subject: Re: [PATCH v9 0/4] iommu: Standardize ATS robustness and state tracking Message-ID: References: <20260615235037.259909-1-praan@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260615235037.259909-1-praan@google.com> On Mon, Jun 15, 2026 at 11:50:33PM +0000, Pranjal Shrivastava wrote: > The primary motivation for this series is an ATS state mismatch observed > under heavy load (via iova_stress). A failure in pci_enable_ats() leaves > IOMMU drivers like arm-smmu-v3 with inconsistent state leading to PCI core > warnings during device detach. > > While David's recent work [1] addressed a discovery race for specific > quirked devices by moving them to the HEADER phase, gaps remained > regarding how Virtual Functions (VFs) inherit state from their Physical > Functions (PFs). Specifically, pci_ats_supported() did not account for > PF-level quirked status, and pci_prepare_ats() lacked STU validation for > VFs. > > Based on discussion with Jason and Baolu in v3/v5, it was decided that the > IOMMU drivers should explicitly check pci_ats_supported() before calling > pci_prepare_ats(). To enforce this, pci_prepare_ats() now noisily checks > for support via WARN_ON(). Furthermore, the device probe should fail if > pci_prepare_ats() fails. Since these early gates preclude software > configuration errors, any remaining failure during pci_enable_ats() is > treated as a kernel bug. > > Following the discussion with the community, the driver-specific series > have been posted separately: > > - Intel IOMMU fixes reported by Sashiko [2] > - Refactors for AMD IOMMU [3] > > [1] https://lore.kernel.org/linux-pci/20260403222750.1215002-1-dmatlack@google.com/ > [2] https://lore.kernel.org/all/20260531170254.60493-1-praan@google.com/ > [3] https://lore.kernel.org/all/20260601134204.2150602-1-praan@google.com/ > > [v9] > - Collected R-b tags from Bjorn, Jason, Nicolin & Sami > - Folded in the dev_err into the WARN for arm-smmu-v3 > [...] > Pranjal Shrivastava (4): > PCI/ATS: Ensure pci_ats_supported() is PF-aware for VFs > PCI/ATS: Validate STU for VFs in pci_prepare_ats() > iommu/arm-smmu-v3: Standardize ATS enablement failure reporting > iommu/vt-d: Fail probe on ATS configuration failure > > drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 9 +++++++-- > drivers/iommu/intel/iommu.c | 15 ++++++++++++--- > drivers/pci/ats.c | 13 ++++++++++--- > 3 files changed, 29 insertions(+), 8 deletions(-) > > > base-commit: 6666bde33b83cb4fc9b1f7ba6a3471479f76ce72 Hi Joerg / Will, Gentle ping on this, please LMK if anything else needs to be done for this seris? Thanks, Praan