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Wed, 21 Oct 2026 19:28:10 -0700 (PDT) Received: from 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa ([173.174.112.101]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4a7d5eb8fc0sm3431624fac.1.2026.10.21.19.28.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 19:28:10 -0700 (PDT) Message-ID: <6ad974ba.a8122b97.39a7e6.f867@mx.google.com> From: karim.sabar@utexas.edu To: matthew.brost@intel.com Subject: Re: [PATCH] drm/xe: Use kvmalloc for the VMA ops page-table update array Date: Wed, 21 Oct 2026 21:28:08 -0500 Cc: thomas.hellstrom@linux.intel.com, rodrigo.vivi@intel.com, airlied@gmail.com, simona@ffwll.ch, intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org In-Reply-To: References: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Hey Matthew! Sounds good to me, the fallback of trying to bind the vma one at a time sound= s good to me. And it is actually a bit broader than my patch since it covers = the -ENOBUFS case as well. It should also be easy to get through drm-xe-fixes= and then backported the normal way. I can write it as a v2 & test it on my Panther Lake device, I have a small re= pro that does about 20,000 mappings and fails after suspend (every time witho= ut the fix). If you'd prefer to write it, I can test your patch as well. Thanks, Karim On Wed, 21 Oct 2026 11:57:48 -0700, Matthew Brost wrote: > On Tue, Oct 20, 2026 at 07:08:27PM -0500, karim.sabar@utexas.edu wrote: >> From: Karim Sabar >>=20 > > Thanks for the patch. I do see the problem in the old code. > Unfortunately, we will not be able to pull this into drm-xe-next or > drm-xe-fixes, as 7.3 is already out and 0e33330f1238 is included in our > 7.4 PR. As a result, this would need to go directly to stable. > > There is also a risk that predates the series containing 0e33330f1238. > If the bind has to run on the GPU, you can still get -ENOBUFS later in > the bind pipeline if the bind is too large to fit into the > migration-layer BB. If that occurs, the proper fix may actually be in > xe_vm_validate_rebind(). If xe_vm_rebind() fails with -ENOBUFS or > -ENOMEM, we could call a new function, such as xe_vm_rebind_iterative(), > which would run each VMA requiring a rebind in its own job. This is > effectively what Mesa does in userspace when a bind operation returns > -ENOBUFS. > > We could probably still pull that approach into drm-xe-fixes + have > naturally backport to stable, and it may ultimately be the better > solution. > > Let me know what you think. I can give this an RB, but I'd like to hold > off until we've settled on the solution we want to pursue here. > > Matt > >> Big games die after every s2idle resume on flat-CCS iGPUs. The exec >> ioctl keeps returning -ENOMEM even with 11-16 GB of RAM free. >>=20 >> On suspend xe_bo_evict_all_user() evicts every user BO in XE_PL_TT on >> these parts. On resume the first exec rebinds every VMA in one go and >> xe_vma_ops_alloc() kmallocs one 384-byte op per VMA as a single array. >> Final Fantasy VII Rebirth has about 33,500 VMAs which means a 12.9 MB >> array. It's over the 4 MB KMALLOC_MAX_SIZE and can never succeed. >> __GFP_NOWARN keeps it out of dmesg. >>=20 >> Data from a Panther Lake handheld (SteamOS kernel 7.2.7), kretprobes >> after resume: >> xe_vma_ops_alloc -ENOMEM on 63 of 63 attempts >> xe_vm_rebind -ENOMEM on 63 of 63 attempts >> BO validate, TTM populate, PT prepare never failed >>=20 >> The array is only used by the CPU and doesn't need to be contiguous. >> This switches it to kvmalloc and kvfree. >>=20 >> With the same change applied as a module on that kernel, the game >> survives every sleep I tried with zero ENOMEM. The biggest array was >> 30,753 ops (11.8 MB). >>=20 >> drm-xe-next already does this through commit 0e33330f1238 ("drm/xe: Add >> struct xe_pt_job_ops"), but that's part of a big series that won't go >> to stable. >>=20 >> I tracked this down and tested it on my own device. I used an AI >> assistant to help with the debugging, i.e the kprobe tracing and >> reading through the xe code. I ran every test, picked the fix and >> reviewed the change myself. >>=20 >> What I couldn't do: this is build-tested on drm-xe-fixes but only >> run-tested on the SteamOS 7.2.7 kernel through an equivalent module, >> not on a mainline kernel. >>=20 >> Fixes: 2e524668c440 ("drm/xe: Add xe_vm_pgtable_update_op to xe_vma_ops") >> Cc: stable@vger.kernel.org # v6.11+ >> Assisted-by: Claude:claude-opus-5-5 >> Signed-off-by: Karim Sabar >> --- >> Downstream SteamOS report with the same data: https://github.com/ValveSoft= ware/SteamOS/issues/2962 >> --- >> drivers/gpu/drm/xe/xe_vm.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >>=20 >> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c >> index 99e42bd29..5caef443b 100644 >> --- a/drivers/gpu/drm/xe/xe_vm.c >> +++ b/drivers/gpu/drm/xe/xe_vm.c >> @@ -703,9 +703,9 @@ static int xe_vma_ops_alloc(struct xe_vma_ops *vops, b= ool array_of_binds) >> continue; >> =20 >> vops->pt_update_ops[i].ops =3D >> - kmalloc_objs(*vops->pt_update_ops[i].ops, >> - vops->pt_update_ops[i].num_ops, >> - GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN); >> + kvmalloc_objs(*vops->pt_update_ops[i].ops, >> + vops->pt_update_ops[i].num_ops, >> + GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN); >> if (!vops->pt_update_ops[i].ops) >> return array_of_binds ? -ENOBUFS : -ENOMEM; >> } >> @@ -742,7 +742,7 @@ static void xe_vma_ops_fini(struct xe_vma_ops *vops) >> xe_vma_svm_prefetch_ops_fini(vops); >> =20 >> for (i =3D 0; i < XE_MAX_TILES_PER_DEVICE; ++i) >> - kfree(vops->pt_update_ops[i].ops); >> + kvfree(vops->pt_update_ops[i].ops); >> } >> =20 >> static void xe_vma_ops_incr_pt_update_ops(struct xe_vma_ops *vops, u8 til= e_mask, int inc_val) >>=20 >> --- >> base-commit: d2ce8fcd778ee6d92748c92d23a56d4416c29d86 >> change-id: 20261020-xe-kvmalloc-vma-ops-2637ebf81cfd >>=20 >> Best regards, >> -- =20 >> Karim Sabar >>