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Tsirkin" , Alex Williamson , Tushar Dave , =?utf-8?Q?C=C3=A9dric?= Le Goater , Ard Biesheuvel , "devel@edk2.groups.io" , qemu-devel@nongnu.org, Shameer Kolothum , qemu-arm@nongnu.org, Peter Maydell , marcel.apfelbaum@gmail.com Subject: Re: [edk2-devel] [RFC PATCH 0/8] hw/arm/virt, hw/pci: PCI pre-enumeration and fixed BAR allocation Message-ID: <20260513113641.GD7655@nvidia.com> References: <20260508183717.193630-1-tdave@nvidia.com> <22cf37c2-b2b1-40db-b8b7-393b6c36a921@app.fastmail.com> <20260512170650.4551c9f6@nvidia.com> <20260512191140-mutt-send-email-mst@kernel.org> <382877be-edad-4eca-a646-a75e1654747f@app.fastmail.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <382877be-edad-4eca-a646-a75e1654747f@app.fastmail.com> X-ClientProxiedBy: YT4PR01CA0403.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:108::17) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9620:EE_|DS0PR12MB8072:EE_ X-MS-Office365-Filtering-Correlation-Id: bc46fd39-c23c-4f88-f4cf-08deb0e3e7c8 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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envelope-from=jgg@nvidia.com; helo=PH0PR06CU001.outbound.protection.outlook.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org On Tue, May 12, 2026 at 05:57:19PM -0600, Alex Williamson wrote: > On Tue, May 12, 2026, at 5:12 PM, Michael S. Tsirkin wrote: > > On Tue, May 12, 2026 at 05:06:50PM -0600, Alex Williamson wrote: > >> If we agree that homogeneous hierarchies (no mixing of EA and > >> programmable BARs) is a reasonable constraint, and possibly extend that > >> to homogeneous per host bridge to simplify the CRS mapping, we have the > >> following work items: > >> > >> * Extend Linux EA support to program bridge apertures for subordinate > >> homogeneous EA hierarchies. > >> > >> * Develop options to virtualize programmable BARs as EA for vfio-pci > >> devices, if not generically for the benefit of testing. > >> > >> * Implement a way to poke holes in the VM address space and plumb > >> through to account for addresses used by EA devices. > >> > >> * Provide those same ranges to the guest via CRS (but not via DT to > >> EDK2), or alternatively expose them through additional PXB host > >> bridges. > >> > >> Does that shape roughly seem accurate? Are there additional gaps I've > >> missed? Thanks, > > > > just one question why not do it in firmware so windows > > is thinkably also handled? > > I suppose someone could chime in if they have a similar requirement > for Windows guests. Otherwise, the incremental effort to extend > Linux EA support seems smaller, though I also don't know what, if > any support Windows has for EA to bother. Regardless, improving > Linux EA support might help elsewhere and doesn't preclude edk2 > support in the future. Thanks, I think there are specific already deployed distros that need to work under qemu though - so I would discount anything that needs kernel changes to work Jason