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Peter Anvin" References: <20260806015233.202486-1-jason.andryuk@amd.com> <083db883-558a-4000-b404-bf170c8309ee@suse.com> <62b5117f-928d-4908-9217-cc16d9cf15f9@suse.com> <967208c9-8d51-4380-8cb4-298f5c313d35@suse.com> Content-Language: en-US From: Jason Andryuk In-Reply-To: <967208c9-8d51-4380-8cb4-298f5c313d35@suse.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MN1PEPF0000F0E2:EE_|SAWPR12MB999115:EE_ X-MS-Office365-Filtering-Correlation-Id: 519541e7-654c-4ad3-ec19-08def3be0c45 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|82310400026|7416014|1800799024|376014|36860700016|4143699003|56012099006|10067099003|11063799006|22082099003|18002099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(23010399003)(82310400026)(7416014)(1800799024)(376014)(36860700016)(4143699003)(56012099006)(10067099003)(11063799006)(22082099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: IuKYHvvcTRYFO/KZfmFoO/sm6r+TPgmOi/Np8cb7Bhat02kwhhP2Qt63hD/yxQntVyKbkqvfS5i0jrOS2NU72YA6232HMDiJD2G4VvgPZXmODeoqe6KOr1oda/jZRrMu1c6i99o0FfDfeTR9Rm8Ehjx6F5obJzESmtBLlkBOlOqBmxpKbKiiK7exXj8EYDDRpPOE0atZM52ca2+oE/7uZxAt6QpKk5fuqdBUfWxbdP+R1OH0mwlDuiHg3JlkD+eKASC9kmO2zsbhxn7Xzv5qt1CCBzMN/IZkY+Oi5U2PJLajPniUAYHTKSFm+iwsuN4k7DB+IcvinwIzfE+3y6a7GHqz0mgpqz9AJZvOqBevlAab4hgW6eWCcIHC5VxatK96eS9fez8fS5yL31epkGRvfduKVTZIRTMkdyJBIxELh+4kOXdK7rUuc/MJdhTlrO9X X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Aug 2026 13:24:30.7985 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 519541e7-654c-4ad3-ec19-08def3be0c45 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MN1PEPF0000F0E2.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SAWPR12MB999115 On 2026-08-06 08:00, Jürgen Groß wrote: > On 06.08.26 13:31, Jan Beulich wrote: >> On 06.08.2026 12:55, Juergen Gross wrote: >>> On 06.08.26 03:52, Jason Andryuk wrote: >>>> Allow disabling XEN_PVHVM for a PV-only.  A stub in the event channel >>>> code needs to be fixed first. >>>> >>>> Jason Andryuk (2): >>>>     xen/events: Fix xen_set_upcall_vector stub >>>>     xen/Kconfig: select XEN_PVHVM >>>> >>>>    arch/x86/xen/Kconfig             | 8 +++++--- >>>>    drivers/xen/events/events_base.c | 2 +- >>>>    2 files changed, 6 insertions(+), 4 deletions(-) >>>> >>> >>> I did a comparison of a kernel built with your patches disabling >>> XEN_PVHVM >>> and my patches with XEN_PVHVM_GUEST disabled. >>> >>> The kernel built with my patches is 6 bytes smaller than the one with >>> your >>> patches. >> >> Isn't this a sign of something else needing tweaking, somewhere? > > This is a sign that there are probably only very few really HVM specific > paths > (in the sense of: explicitly not marked as irrelevant for PV) in the > kernel. > Yes, I'm sure you can find some more, but I'm really not sure this is > relevant > for more than a handful of users. I see more reduction: 15029248 - arch/x86/boot/bzImage 15021056 - arch/x86/boot/bzImage.after ~8k 52542480 - vmlinux 52523184 - vmlinux.after ~18k $ ../linux/scripts/bloat-o-meter vmlinux vmlinux.after add/remove: 1/136 grow/shrink: 14/48 up/down: 15902/-22430 (-6528) >>> So I don't see any reason to take your patches, which conflict with >>> mine, >>> especially as my patches have a negative diffstat on source level, too. >> >> Hmm, Jason's patches look to move things into a more adequate direction, >> though. In which case I think a negative diffstat becomes an irrelevant >> argument? > > Depends on what you are looking for. > > My take from this is that a PV-only kernel with Jason's patches is not > really > adding any value, while my simplification is at least making things simpler > in terms of code volume and number of Xen related config options. > > Of course it would be possible to have a smaller PV-only kernel, but as > I said > already, there has been no public demand for that in the last years and the > downsides IMHO far outweigh the potential gain. > > IMO the "adequate direction" regarding Xen specific kernel code is > towards PVH > and not towards more PV specific tweaking. And I'm very sure the kernel > community outside of the Xen community is agreeing with me here. I don't need PV-only kernels, so I am fine with not pursuing this patch set. Mainly I wanted to post this alternative since restoring PV-only is possible (and I inadvertently broke it). Converting CONFIG_XEN_PVHVM to CONFIG_XEN looked wrong when it didn't apply to PV. Pursuing your patches for the reasons you give also makes sense. Regards, Jason