From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 66882366042; Fri, 22 May 2026 17:59:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779472747; cv=none; b=PjtOsh7mirvDLZjCq3n9XYkrvOKvO6YM0c2jqhUBHOIHgNJj08gpBV205KLLoECP/OX43RptPSTybqBaehjIhje5An2ui0ujWpzb9Dis4fscg7quqMxmScM9eNEMvXa+hSuNyU/aj857mfmEPu2lTZq1D3MjCqzFDICoa1ZFchs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779472747; c=relaxed/simple; bh=8e922+jS//8NGIWTqfOW6k7zG1zpaE4rZo0LrZTDT+8=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=YTuAcztSZw2kGyvqMv9cl170SP+E+6KUDIXnnDmdD4hmOZ+YlWvOW6WXKv2BNgR7fmQ0+See27pDKZXjTEoC4BxSPDioklwtPyn3CjJECvcRBy/sGhmvJOtIRUUxoqVTNfVfG2kCQQCxjG5N2FNwT695rQOfbLEkqZ8pKML+gio= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R/lF87yY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="R/lF87yY" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id 23DC41F000E9; Fri, 22 May 2026 17:59:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779472746; bh=QvhytzGMgy3nE/I3M4lZRHo1Fz4WHKJA8K2mHNM+zQY=; 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> 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 Content-Disposition: inline In-Reply-To: <20260512184846.119396-6-dmatlack@google.com> 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)