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[34.142.211.105]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a49858c123sm538411a91.3.2026.09.28.10.19.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 10:19:49 -0700 (PDT) Date: Mon, 28 Sep 2026 17:19:41 +0000 From: Pranjal Shrivastava To: David Matlack Cc: kexec@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Adithya Jayachandran , Alexander Graf , Alex Williamson , Bjorn Helgaas , Chris Li , David Rientjes , Jacob Pan , Jason Gunthorpe , Jonathan Corbet , Josh Hilke , Leon Romanovsky , Lukas Wunner , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pratyush Yadav , Randy Dunlap , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Subject: Re: [PATCH v9 09/13] PCI: liveupdate: Adopt ACS controls in incoming preserved devices Message-ID: References: <20260918200640.887030-1-dmatlack@google.com> <20260918200640.887030-10-dmatlack@google.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260918200640.887030-10-dmatlack@google.com> On Fri, Sep 18, 2026 at 08:06:35PM +0000, David Matlack wrote: > Adopt Access Control Services (ACS) controls on all incoming preserved > devices (endpoints and upstream bridges) during a Live Update. > > Inheriting ACS flags avoids changing routing rules while memory > transactions are in flight from preserved devices. This is also strictly > necessary to ensure that IOMMU group assignments do not change during or > after Live Update. > > The adopted controls are recorded by the pci_save_state() call in > pci_bus_add_device(), which runs before drivers bind, so they are > automatically reapplied by pci_restore_state() if the device is reset. > If that save buffer could not be allocated there is nowhere to record > the adopted controls, and they would be silently lost by the first > reset. Program ACS from scratch in that case, which is a better outcome > than leaving ACS disabled. > > To simplify ACS inheritance, reject preserving any devices that require > quirks to enable ACS as those quirks would also have to take Live Update > into account. > > Signed-off-by: David Matlack Reviewed-by: Pranjal Shrivastava Thanks, Praan