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[34.127.87.210]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39645da08desm723671a91.17.2026.08.24.13.02.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2026 13:02:48 -0700 (PDT) Date: Mon, 24 Aug 2026 20:02:45 +0000 From: Samiullah Khawaja 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 , Pranjal Shrivastava , Pratyush Yadav , Saeed Mahameed , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Subject: Re: [PATCH v8 11/12] PCI: liveupdate: Do not disable bus mastering on preserved devices during kexec Message-ID: References: <20260728221007.2098560-1-dmatlack@google.com> <20260728221007.2098560-12-dmatlack@google.com> Precedence: bulk X-Mailing-List: linux-doc@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: <20260728221007.2098560-12-dmatlack@google.com> On Tue, Jul 28, 2026 at 10:10:05PM +0000, David Matlack wrote: >Do not disable bus mastering on outgoing preserved devices during >pci_device_shutdown() for kexec. > >Preserved devices must be allowed to perform memory transactions during >a Live Update to ensure continuous operation. Clearing the bus >mastering bit would prevent these devices from issuing any memory >requests while the new kernel boots. > >Because bridges upstream of preserved endpoint devices are also >automatically preserved, this change also avoids clearing bus mastering >on them. This is critical because clearing bus mastering on an upstream >bridge prevents the bridge from forwarding memory requests upstream (i.e. >it would prevent the endpoint device from accessing system RAM and doing >peer-to-peer transactions with devices not downstream of the bridge). > >Reviewed-by: Pranjal Shrivastava >Reviewed-by: Pasha Tatashin >Signed-off-by: David Matlack >--- > drivers/pci/liveupdate.c | 11 +++++++++++ > drivers/pci/liveupdate.h | 6 ++++++ > drivers/pci/pci-driver.c | 7 +++++-- > 3 files changed, 22 insertions(+), 2 deletions(-) > Reviewed-by: Samiullah Khawaja