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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2025 16:03:47.3062 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 53636b5f-8fb1-45e1-3fc6-08dd8bee6b4f X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DS1PEPF0001708E.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB7673 On Mon, May 05, 2025 at 12:55:05PM -0300, Jason Gunthorpe wrote: > On Mon, May 05, 2025 at 08:44:22AM -0700, Nicolin Chen wrote: > > On Mon, May 05, 2025 at 12:01:09PM -0300, Jason Gunthorpe wrote: > > > On Mon, Apr 28, 2025 at 10:41:45AM -0700, Nicolin Chen wrote: > > > > > I'm uncertain, but perhaps pr_warn_ratelimited() would be a better > > > > > alternative to WARN_ON() here? WARN_ON_ONCE() generates warning messages > > > > > with kernel call traces in the kernel messages, which might lead users > > > > > to believe that something serious has happened in the kernel. > > > > > > > > We already have similar practice, e.g. iommufd_hwpt_nested_alloc. > > > > > > > > In my review, a WARN_ON/WARN_ON_ONCE means there is a kernel bug, > > > > which shouldn't occur in the first place and isn't something that > > > > > > Right, so it should never happen from any ioctl path and syzkaller > > > should never trigger it based on system call randomization > > > > > > Is that what this achieves? > > > > The functions would be still used in the kernel path. So, I think > > we need to retain these warnings for that. But given that an ioctl > > could trigger a series of WARN_ONs, WARN_ON_ONCE is something that > > wouldn't bother user space a lot while it provides the kernel path > > enough info to debug. > > No, it does bother userspace, we must not have ioctl triggerable > WARN_ON at all. You mean we have to eliminate any WARN_ON in a call path of an ioctl? We can drop them, just that would mute any kernel bug. Btw, IIRC, the destroy ioctl could trigger some WARN_ON in the remove() when the object's refcount isn't correctly decreased. Should that be a problem too? Thanks Nicolin