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h=Date:From:To:Cc:Subject:In-Reply-To; b=R/lF87yYK3T8ZgihOcJLjT1tJ2iqucYpoTXz+lE+iNM8GsdPFgTHohAXTIRWiXCaq Z3sLJcXDGLxdXpbjd5vXsU6R9vl67LHiffd1HrCgb9F7RXCuMOOfdz7pnSMbp79xKx bqeV2FB/iwmC+djHEZ5mqJS5Do9oSrdFTfzKqDljYArEUikYmdVLSGNtDVRe2CbZXe nSlHxZCLg/t15FV7B3ebQdjPPEJOXYtquDgAXX27hU8eVFNYP8lGHAlA4FwFKLJOmb 9sPWoEQ7WIovdqVHFNJR3cl90/fD+OjTmJ5s3ncJReREDo+cltiTIVjISJ3mzjWVrW j+eMJNK+bTxAw== Date: Fri, 22 May 2026 12:59:05 -0500 From: Bjorn Helgaas 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 , Samiullah Khawaja , Shuah Khan , Vipin Sharma , William Tu , Yi Liu Subject: Re: [PATCH v5 05/11] PCI: liveupdate: Keep bus numbers constant during Live Update Message-ID: <20260522175905.GA232400@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512184846.119396-6-dmatlack@google.com> X-Rspamd-Server: rspam11 X-Stat-Signature: 19mmpyixfpph7gaq46o43pa71dtbbi55 X-Rspamd-Queue-Id: 4392340005 X-Rspam-User: X-HE-Tag: 1779472747-663894 X-HE-Meta: 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 wUPYJ/KO UIIQUJ2z0xtni/8AUNZKX/Gas/hJ85ZaH2g1KWBDv+APQHSw7q1DkPbPljTHGWIE7VibnAbtasf18Od1dzsUnTwifdIr6OuEJuXzDXwnb0klyqdS2D0b5OSUWhuE2QYgHz3HuX+sB7WyHGTeOOuH/zknf3E5kB6cv+0938pf93Qb6mKCjPhq8lkTvGqp1DTPAlivtGCvU/I9so7i4sjlBUznSww== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, May 12, 2026 at 06:48:40PM +0000, David Matlack wrote: > ... > + * The PCI core guarantees that preserved devices can be identified by the same > + * bus, device, and function numbers for as long as they are preserved > + * (including across kexec). To accomplish this, the PCI core always inherits > + * the secondary and subordinate bus numbers assigned to bridges during scanning > + * if any device is preserved. This is true even on architectures that always > + * assign new bus numbers during scanning. The kernel assumes the previous > + * kernel established a sane bus topology across kexec. > + * > + * If a misconfigured or unconfigured bridge is encountered during enumeration > + * while there are preserved devices, itss secondary and subordinate bus numbers > + * will be cleared and devices below it will not be enumerated. s/itss/its/ > + * To keep things simple, inherit the secondary and subordinate bus numbers on > + * _all_ bridges if _any_ PCI devices are preserved (i.e. even bridges without > + * any downstream endpoints that were preserved). This avoids accidentally > + * assigning a bridge a new window that overlaps with a preserved device that is > + * downstream of a different bridge. s/i.e. even/i.e. even/ (remove extra space)