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pr=C Message-ID: Date: Wed, 27 Aug 2025 10:03:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 8/8] xen/dom0less: store xenstore event channel in page To: Jason Andryuk , CC: Stefano Stabellini , Julien Grall , Bertrand Marquis References: <20250826210847.126015-1-jason.andryuk@amd.com> <20250826210847.126015-9-jason.andryuk@amd.com> From: "Orzel, Michal" Content-Language: en-US In-Reply-To: <20250826210847.126015-9-jason.andryuk@amd.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Received-SPF: None (SATLEXMB03.amd.com: michal.orzel@amd.com does not designate permitted sender hosts) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL02EPF00021F69:EE_|MN0PR12MB5956:EE_ X-MS-Office365-Filtering-Correlation-Id: 8199a553-4515-45ed-5f17-08dde5402bd0 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|376014|36860700013; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Aug 2025 08:03:13.1781 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 8199a553-4515-45ed-5f17-08dde5402bd0 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF00021F69.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB5956 On 26/08/2025 23:08, Jason Andryuk wrote: > Write the associated event channel into the xenstore page so xenstored > can read it. xenstored can map the grant by the reserved grant table > entry, and then read out the event channel and bind it. This eliminates > the need for an additional mechanism to discover the event channel. > > Signed-off-by: Jason Andryuk > --- > v2: > No change > > This should go in after the init-dom0less changes so init-dom0less is > ready for xenstored automatically introducing domains. > > I'm looking for feedback. This is ARM-only for the time being, but that > is the only in-tree user of this code. From the perspective, it is okay > to go in. > > If we want a cross-arch approach, a common function to write to guest > physical addresses would be needed for additional arches, but they > aren't available yet. > > Oleksii added a function pointer to dtb_load() and initrd_load() when > moving dom0less to common, but I think that isn't necessary. Just > having a common helper would be sufficient. > > copy_to_guest_phys() or something_copy_to_guest_phys() could be defined > or a wrapper for ARM's copy_to_guest_phys_flush_dcache(). Other arches > could need to implement it when using dom0less. > > I'm not an ARM expert, but Stefano said > copy_to_guest_phys_flush_dcache() is not necessary since this xenstore > page isn't expected to be accessed without caches enabled. I'm not sure I understand this point. When copying data *to* the guest, cleaning is about Xen's cache, not guest's... ~Michal