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client-ip=165.204.84.17; helo=satlexmb08.amd.com; pr=C Received: from satlexmb08.amd.com (165.204.84.17) by CY4PEPF0000E9DC.mail.protection.outlook.com (10.167.241.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.339.3 via Frontend Transport; Wed, 19 Aug 2026 18:36:38 +0000 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Wed, 19 Aug 2026 13:36:38 -0500 Received: from [172.19.71.207] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.45 via Frontend Transport; Wed, 19 Aug 2026 13:36:37 -0500 Message-ID: Date: Wed, 19 Aug 2026 11:36:37 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] accel/amdxdna: return early from a zero-length flush Content-Language: en-US From: Lizhi Hou To: Taimuraz Kaitmazov , , CC: , , References: <20260817230655.356785-1-taimuraz@kaitmazov.com> In-Reply-To: Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: xm7mmX6EVbqJgo82e5sPIAqLPgsCiR3bMpz5JJnY7C8zFwkCROFw8zzreBhkh/uEBbJnya7abvSxnQ0RUCloKhpE3FyllxFIWPi4a2G/Uge1DYk5pjo9HPtZliNaJrAq4rGTUXJalbFLh7+RUO92saud11+NGAz80O9yuKxCozn6NQRh+JhRiiGQ3fTzcaRUWRqarmtEgOJO59gdj9GiAYqRhA+nLUV5KWCuNhGCKczhPAQcLqVPU7OXrGp99LtQH/ELt49GPGlaQF6+1qjxnmGbnKvsof51leE8kvmI096a6vdz9v+rSm4UIsGSslW195lfRgntRJbFxZSZ8w2pgXbot0bN+TBd/Zpodeua7765AzDLgeirJbzPfDbpnntKFZ6VNoub1EhkhS3AmDlgHYgBGkmol5+q/g1/KicmsdAOxkzz8IRuJmtQ6yu/if2O X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Aug 2026 18:36:38.5060 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 15a97b96-4e78-426b-9a41-08defe20ce42 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=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000E9DC.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9408 Applied to drm-misc-fixes On 8/18/26 09:23, Lizhi Hou wrote: > > On 8/17/26 16:06, Taimuraz Kaitmazov wrote: >> SYNC_BO does not constrain its size, so a request for zero bytes reaches >> drm_clflush_virt_range(), which ends with an unconditional >> clflushopt(end - 1). For an empty range that is the byte before the >> mapping, and abo->mem.kva comes from vmap(), so the access lands in the >> guard page below the vmalloc area and faults: >> >>    BUG: unable to handle page fault for address: ffffd16fbbc70fff >>    #PF: supervisor read access in kernel mode >>    Oops: Oops: 0000 [#1] SMP NOPTI >>    CPU: 7 UID: 1000 Comm: sync_bo_probe >>    RIP: 0010:drm_clflush_virt_range+0x3c/0x70 >>    Call Trace: >>     amdxdna_drm_sync_bo_ioctl+0x124/0x430 [amdxdna] >>     drm_ioctl+0x301/0x4c0 >>     __x64_sys_ioctl+0x115/0x2f0 >>     do_syscall_64+0xa6/0x3d0 >> >> Any process that can open the render node can do this. Reproduced 3 of 3 >> times on a Strix Point NPU (1022:17f0), by calling SYNC_BO with size >> 0 on >> an AMDXDNA_BO_SHARE object. The import arm takes the same request but >> flushes the whole scatterlist, so it survives it. >> >> Nothing needs flushing for an empty range, so answer before choosing a >> path. >> >> Fixes: e252e3f3488a ("accel/amdxdna: Revise device bo creation and >> free") >> Cc: stable@vger.kernel.org >> Signed-off-by: Taimuraz Kaitmazov >> --- >> Trees before amdxdna_flush_bo() existed carry the same call inline in >> amdxdna_drm_sync_bo_ioctl(), with args->size passed to >> drm_clflush_virt_range() unclamped, so a backport wants the guard at >> that >> call site instead. >> >>   drivers/accel/amdxdna/amdxdna_gem.c | 3 +++ >>   1 file changed, 3 insertions(+) >> >> diff --git a/drivers/accel/amdxdna/amdxdna_gem.c >> b/drivers/accel/amdxdna/amdxdna_gem.c >> index 1c63eff0a4a8..2a16de96e6a4 100644 >> --- a/drivers/accel/amdxdna/amdxdna_gem.c >> +++ b/drivers/accel/amdxdna/amdxdna_gem.c >> @@ -1247,6 +1247,9 @@ static int amdxdna_flush_bo(struct >> amdxdna_gem_obj *abo, u64 offset, u64 size) >>           return -EINVAL; >>         size = min(abo->mem.size, end) - offset; >> +    if (!size) >> +        return 0; >> + > Reviewed-by: Lizhi Hou >>       if (is_import_bo(abo)) >>           drm_clflush_sg(abo->base.sgt); >>       else if (amdxdna_gem_vmap(abo))