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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> 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> X-Rspamd-Queue-Id: 1AC79180003 X-Stat-Signature: 7qdityxb9mjdnumrspcaj7fatnnd3gyh X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1787601770-767073 X-HE-Meta: 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 78dyNpRg kGk4S+q90CR+6OV64z3qk6S0F5Dn9A8sJPOUOAir3HL0SzuhX4qFassPJO62vc/st5/8t62KkD8epjXBRvPSpP2yIP54OHB1EamMLtOcLt3foUIeBp4BdPUGKWmVMxbPeRdN0FOnyuFD2koEdz+fqr9LWQPiDHjftb+pMXvrLv5Ly7Ijb4HqBZhARMZLyfMaDm+/Jsoda2uuNKLE1V+RC4R6QSxu0nkuVgtp633FV0cr2GDCuWD2fIPvrFRk361fmUB8Md/Nc1NK9qUrUExx4RRHrZxTQ59T0L8n3lxQu7DlJTIFNDcBlSpo0i03KpKjzM2xxQMgDTiBba6r5MMqnFeiFvyIjUGMa+oiz7yQTfIQaWyhUdGAErd5FnNQlSlru6lIZ0aPt6As1DAFY2YZ1A8CklrQW+RFCrglV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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