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b=KN3WnNG6ESqaiUtKkFDTZzH5NwOfPaEq3SyKjlnj2BVvSVQdzrUGi+rO3bBGnd9Ho LpbZbnimfO8+EWuNKwp9Kq/5DffXALvIy8g8aExAHiolfdguYmdbVu0XP84pBoVoDG 2ANaWg1zO/7DOmKgmZKDkcv1ZqdjQpAE9igTSVdboUsROFqdafQ4Ta1ZmMLSBkwm5g zQZOt3jfGQKtw6ZQ2AYAzx6QVBaEg7bthNexA/udyyfyBqcl3NkKXPxr3odyqMidAa N9Jhv8lkZdyJYuDO5Mg8YthFxaBnptnFCNCrWT2+YaGtcpTMCUtsROxDVq68gXD+2b uimsyOI0k4irQ== Date: Wed, 25 Feb 2026 16:47:46 -0600 From: Bjorn Helgaas To: David Matlack Cc: Alex Williamson , Adithya Jayachandran , Alexander Graf , Alex Mastro , Alistair Popple , Andrew Morton , Ankit Agrawal , Bjorn Helgaas , Chris Li , David Rientjes , Jacob Pan , Jason Gunthorpe , Jason Gunthorpe , Jonathan Corbet , Josh Hilke , Kevin Tian , kexec@lists.infradead.org, kvm@vger.kernel.org, Leon Romanovsky , Leon Romanovsky , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, Lukas Wunner , =?utf-8?Q?Micha=C5=82?= Winiarski , Mike Rapoport , Parav Pandit , Pasha Tatashin , Pranjal Shrivastava , Pratyush Yadav , Raghavendra Rao Ananta , Rodrigo Vivi , Saeed Mahameed , Samiullah Khawaja , Shuah Khan , Thomas =?utf-8?Q?Hellstr=C3=B6m?= , Tomita Moeko , Vipin Sharma , Vivek Kasireddy , William Tu , Yi Liu , Zhu Yanjun Subject: Re: [PATCH v2 03/22] PCI: Inherit bus numbers from previous kernel during Live Update Message-ID: <20260225224746.GA3714478@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260129212510.967611-4-dmatlack@google.com> X-Stat-Signature: y5in9c1u66ni6bu4oofoj3ox3s7wpeod X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: 2A76E40004 X-HE-Tag: 1772059668-190482 X-HE-Meta: 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 iqNewYT8 y5RC8CS7o34b9eXXsHRXHyVcL3wWTKLgIG3cudV1qvpeLbwHsVcJzLwhY78RQZ664Gv4rY/SjGn6HfDE0yvH+BL/Jy0Zb2QZygee7Q6gBa663nQO8iqyy1NaLJptQv7+Mv8E9N7BOevHM2voasLJkDZdvmDCPn7M42Juv+UBhLkuMIwc6OZBLu9naiojMy0/5tNS6cCDTAcffGnhhx+OTWrUIbz6dEtsTirbGXpjI373o7ZHNL4eIhjV1GWFN4zflC43E Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jan 29, 2026 at 09:24:50PM +0000, David Matlack wrote: > Inherit bus numbers from the previous kernel during a Live Update when > one or more PCI devices are being preserved. This is necessary so that > preserved devices can DMA through the IOMMU during a Live Update > (changing bus numbers would break IOMMU translation). I think changing bus numbers would break DMA regardless of whether an IOMMU is involved. Completions carrying the data for DMA reads are routed back to the Requester ID of the read.