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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 BL02EPF00021F6A.mail.protection.outlook.com (10.167.249.6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.339.3 via Frontend Transport; Tue, 18 Aug 2026 16:23:43 +0000 Received: from satlexmb07.amd.com (10.181.42.216) 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; Tue, 18 Aug 2026 11:23:43 -0500 Received: from [172.19.71.207] (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server id 15.2.2562.45 via Frontend Transport; Tue, 18 Aug 2026 11:23:43 -0500 Message-ID: Date: Tue, 18 Aug 2026 09:23:37 -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 To: Taimuraz Kaitmazov , , CC: , , References: <20260817230655.356785-1-taimuraz@kaitmazov.com> From: Lizhi Hou In-Reply-To: <20260817230655.356785-1-taimuraz@kaitmazov.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: hJ1kLWWgX1u5Ai3/5eXFv01s6zyBn+yOhIzNjnWAafja0xnQBoYf+vnpzDWTTX9i3rUArjN100COS8nUvHrGN4lAgqdf2bKRPYoxakWpIu8uui2s6wwyJ8/JzGSjY84WlMUP+GHTCdZO9UlVGcZR6hrIRFe+jmHiRw29E43McNo8LtHERyHJvpjgg2WOSgCAsyIXKM0nsFfsrNFLHj2aV1o/OR8OSw5yKi3g9/SbaCAYZg1kA3Xs9Ph7mPEdiyxWcgdkKXGyYYT8+KL6vX2y7eOvlbOPVqeQQCIKmiwDEyMSBGVhQpgswSR0QoVNkaPSpV7j188vLmBLKZyBm2DOplVe9BTu8+Zq8qBdVcHv4fg/A2FbjDb/hNMoNHwkroUA8Y5MA0v+WcL+ECjHFNVStPfxqT55MJXFlEI0miwyusfE5Rmhjcut1ntSgO6YzVAK X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Aug 2026 16:23:43.8456 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0718aca2-7cdd-4c8e-77d8-08defd45128b 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: BL02EPF00021F6A.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB8743 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))