Message-ID: <CACSVV025zH-T82jp7xfgjKH=UoiJDDDq6xgyVjyrDhSH1=pQ4w@mail.gmail.com>
Date: Mon, 8 Sep 2025 09:19:30 -0700
From: Rob Clark <rob.clark@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>
Cc: Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Jonathan Marek <jonathan@...ek.ca>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] drm/msm: Fix bootup splat with separate_gpu_drm modparam

On Mon, Sep 8, 2025 at 8:42 AM Akhil P Oommen <akhilpo@....qualcomm.com> wrote:
>
> On 9/2/2025 9:25 PM, Rob Clark wrote:
> > On Tue, Sep 2, 2025 at 4:50 AM Akhil P Oommen <akhilpo@....qualcomm.com> wrote:
> >>
> >> The drm_gem_for_each_gpuvm_bo() call from lookup_vma() accesses
> >> drm_gem_obj.gpuva.list, which is not initialized when the drm driver
> >> does not support DRIVER_GEM_GPUVA feature. Enable it for msm_kms
> >> drm driver to fix the splat seen when msm.separate_gpu_drm=1 modparam
> >> is set:
> >>
> >> [    9.506020] Unable to handle kernel paging request at virtual address fffffffffffffff0
> >> [    9.523160] Mem abort info:
> >> [    9.523161]   ESR = 0x0000000096000006
> >> [    9.523163]   EC = 0x25: DABT (current EL), IL = 32 bits
> >> [    9.523165]   SET = 0, FnV = 0
> >> [    9.523166]   EA = 0, S1PTW = 0
> >> [    9.523167]   FSC = 0x06: level 2 translation fault
> >> [    9.523169] Data abort info:
> >> [    9.523170]   ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000
> >> [    9.523171]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
> >> [    9.523172]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> >> [    9.523174] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000ad370f000
> >> [    9.523176] [fffffffffffffff0] pgd=0000000000000000, p4d=0000000ad4787403, pud=0000000ad4788403, pmd=0000000000000000
> >> [    9.523184] Internal error: Oops: 0000000096000006 [#1]  SMP
> >> [    9.592968] CPU: 9 UID: 0 PID: 448 Comm: (udev-worker) Not tainted 6.17.0-rc4-assorted-fix-00005-g0e9bb53a2282-dirty #3 PREEMPT
> >> [    9.592970] Hardware name: Qualcomm CRD, BIOS 6.0.240718.BOOT.MXF.2.4-00515-HAMOA-1 07/18/2024
> >> [    9.592971] pstate: a1400005 (NzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> >> [    9.592973] pc : lookup_vma+0x28/0xe0 [msm]
> >> [    9.592996] lr : get_vma_locked+0x2c/0x128 [msm]
> >> [    9.763632] sp : ffff800082dab460
> >> [    9.763666] Call trace:
> >> [    9.763668]  lookup_vma+0x28/0xe0 [msm] (P)
> >> [    9.763688]  get_vma_locked+0x2c/0x128 [msm]
> >> [    9.763706]  msm_gem_get_and_pin_iova_range+0x68/0x11c [msm]
> >> [    9.763723]  msm_gem_get_and_pin_iova+0x18/0x24 [msm]
> >> [    9.763740]  msm_fbdev_driver_fbdev_probe+0xd0/0x258 [msm]
> >> [    9.763760]  __drm_fb_helper_initial_config_and_unlock+0x288/0x528 [drm_kms_helper]
> >> [    9.763771]  drm_fb_helper_initial_config+0x44/0x54 [drm_kms_helper]
> >> [    9.763779]  drm_fbdev_client_hotplug+0x84/0xd4 [drm_client_lib]
> >> [    9.763782]  drm_client_register+0x58/0x9c [drm]
> >> [    9.763806]  drm_fbdev_client_setup+0xe8/0xcf0 [drm_client_lib]
> >> [    9.763809]  drm_client_setup+0xb4/0xd8 [drm_client_lib]
> >> [    9.763811]  msm_drm_kms_post_init+0x2c/0x3c [msm]
> >> [    9.763830]  msm_drm_init+0x1a8/0x22c [msm]
> >> [    9.763848]  msm_drm_bind+0x30/0x3c [msm]
> >> [    9.919273]  try_to_bring_up_aggregate_device+0x168/0x1d4
> >> [    9.919283]  __component_add+0xa4/0x170
> >> [    9.919286]  component_add+0x14/0x20
> >> [    9.919288]  msm_dp_display_probe_tail+0x4c/0xac [msm]
> >> [    9.919315]  msm_dp_auxbus_done_probe+0x14/0x20 [msm]
> >> [    9.919335]  dp_aux_ep_probe+0x4c/0xf0 [drm_dp_aux_bus]
> >> [    9.919341]  really_probe+0xbc/0x298
> >> [    9.919345]  __driver_probe_device+0x78/0x12c
> >> [    9.919348]  driver_probe_device+0x40/0x160
> >> [    9.919350]  __driver_attach+0x94/0x19c
> >> [    9.919353]  bus_for_each_dev+0x74/0xd4
> >> [    9.919355]  driver_attach+0x24/0x30
> >> [    9.919358]  bus_add_driver+0xe4/0x208
> >> [    9.919360]  driver_register+0x60/0x128
> >> [    9.919363]  __dp_aux_dp_driver_register+0x24/0x30 [drm_dp_aux_bus]
> >> [    9.919365]  atana33xc20_init+0x20/0x1000 [panel_samsung_atna33xc20]
> >> [    9.919370]  do_one_initcall+0x6c/0x1b0
> >> [    9.919374]  do_init_module+0x58/0x234
> >> [    9.919377]  load_module+0x19cc/0x1bd4
> >> [    9.919380]  init_module_from_file+0x84/0xc4
> >> [    9.919382]  __arm64_sys_finit_module+0x1b8/0x2cc
> >> [    9.919384]  invoke_syscall+0x48/0x110
> >> [    9.919389]  el0_svc_common.constprop.0+0xc8/0xe8
> >> [    9.919393]  do_el0_svc+0x20/0x2c
> >> [    9.919396]  el0_svc+0x34/0xf0
> >> [    9.919401]  el0t_64_sync_handler+0xa0/0xe4
> >> [    9.919403]  el0t_64_sync+0x198/0x19c
> >> [    9.919407] Code: eb0000bf 54000480 d100a003 aa0303e2 (f8418c44)
> >> [    9.919410] ---[ end trace 0000000000000000 ]---
> >>
> >> Fixes: 217ed15bd399 ("drm/msm: enable separate binding of GPU and display devices")
> >> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
> >> ---
> >>  drivers/gpu/drm/msm/msm_drv.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> >> index 9dcc7a596a11d9342a515dab694bac93dc2805cb..7e977fec4100792394dccf59097a01c2b2556608 100644
> >> --- a/drivers/gpu/drm/msm/msm_drv.c
> >> +++ b/drivers/gpu/drm/msm/msm_drv.c
> >> @@ -826,6 +826,7 @@ static const struct file_operations fops = {
> >>
> >>  #define DRIVER_FEATURES_KMS ( \
> >>                 DRIVER_GEM | \
> >> +               DRIVER_GEM_GPUVA | \
> >
> > Hmm, the description of DRIVER_GEM_GPUVA is that "Driver supports user
> > defined GPU VA bindings for GEM objects", which isn't really true.
> > Fortunately the only thing that it actually seems to control currently
> > is the list head initialization.
> >
> > Idk if it would be better to make the list head init unconditional, or
> > just add a comment here?
>
> But the KMS-only drm driver do use symbols related to gpuva. "struct
> gpuva" for eg:. From that perspective, shouldn't we select this feature
> here?

Based on how DRIVER_GEM_GPUVA is currently used (ie. not exposed to
userspace, etc) this is fine.  Maybe the comment describing
DRIVER_GEM_GPUVA should be updated to something along the lines of
"Driver uses the drm_gpuvm infrastructure" instead of "Driver supports
user defined GPU VA bindings for GEM object"

BR,
-R

> -Akhil
>
> >
> > BR,
> > -R
> >
> >>                 DRIVER_ATOMIC | \
> >>                 DRIVER_MODESET | \
> >>                 0 )
> >>
> >> --
> >> 2.50.1
> >>
>

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