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Message-ID: <aQ0FkZv_l8UPLhvr@sultan-box>
Date: Thu, 6 Nov 2025 12:31:13 -0800
From: Sultan Alsawaf <sultan@...neltoast.com>
To: "Nirujogi, Pratap" <pnirujog@....com>
Cc: Mario Limonciello <mario.limonciello@....com>, bin.du@....com,
pratap.nirujogi@....com, amd-gfx@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, alexander.deucher@....com,
benjamin.chan@....com, christian.koenig@....com, dantony@....com,
gjorgji.rosikopulos@....com, king.li@....com, phil.jawich@....com
Subject: Re: [PATCH] drm/amd/amdgpu: Ensure isp_kernel_buffer_alloc() creates
a new BO
On Thu, Nov 06, 2025 at 03:08:44PM -0500, Nirujogi, Pratap wrote:
>
>
> On 11/6/2025 1:58 PM, Sultan Alsawaf wrote:
> > Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> >
> >
> > On Thu, Nov 06, 2025 at 12:46:51PM -0600, Mario Limonciello wrote:
> > > On 11/5/25 5:21 PM, Sultan Alsawaf wrote:
> > > > From: Sultan Alsawaf <sultan@...neltoast.com>
> > > >
> > > > When the BO pointer provided to amdgpu_bo_create_kernel() points to
> > > > non-NULL, amdgpu_bo_create_kernel() takes it as a hint to pin that address
> > > > rather than allocate a new BO.
> > > >
> > > > This functionality is never desired for allocating ISP buffers. A new BO
> > > > should always be created when isp_kernel_buffer_alloc() is called, per the
> > > > description for isp_kernel_buffer_alloc().
> > >
> > > Are you just going off descriptions, or is there a problem with reuse?
> >
> > I am going based off the ISP4 driver's usage of isp_kernel_buffer_alloc().
> >
> > This fixes the following crash I experienced on v5 of the ISP4 patchset:
> >
> > [ 175.485627] BUG: unable to handle page fault for address: 00007f6b1092e888
> > [ 175.485799] #PF: supervisor read access in kernel mode
> > [ 175.485840] #PF: error_code(0x0000) - not-present page
> > [ 175.485869] PGD 0 P4D 0
> > [ 175.485889] Oops: Oops: 0000 [#1] SMP
> > [ 175.485908] CPU: 15 UID: 1000 PID: 57022 Comm: cheese Tainted: G U W 6.17.7 #1 PREEMPT
> > [ 175.485921] Tainted: [U]=USER, [W]=WARN
> > [ 175.485933] Hardware name: HP HP ZBook Ultra G1a 14 inch Mobile Workstation PC/8D01, BIOS X89 Ver. 01.03.00 04/25/2025
> > [ 175.485943] RIP: 0010:amdgpu_bo_create_reserved+0xb1/0x1c0 [amdgpu]
> > [ 175.485961] Code: 8b 30 44 89 64 24 20 48 89 44 24 28 c7 44 24 30 01 00 00 00 c7 44 24 1c b8 02 00 00 c6 44 24 08 00 4d 85 f6 0f 84 a9 00 00 00 <49> 8b 86 a8 01 00 00 49 8b be 40 01 00 00 31 f6 48 89 04 24 e8 d6
> > [ 175.485976] RSP: 0018:ffff97b14e097ad0 EFLAGS: 00010202
> > [ 175.485988] RAX: 0000000000000021 RBX: ffff97b085af04d0 RCX: 0000000000000000
> > [ 175.486002] RDX: 0000000000008000 RSI: ffff97b14e097ae0 RDI: ffff97b14e097b20
> > [ 175.486012] RBP: ffff97b085af04c8 R08: ffff97b085af04d8 R09: ffff97b085af04c8
> > [ 175.486023] R10: 0000000000ffffff R11: ffff97b085af0560 R12: 0000000000000002
> > [ 175.486031] R13: ffff97b085af04d8 R14: 00007f6b1092e6e0 R15: ffff97b0a0f00000
> > [ 175.486037] FS: 00007faf60ffe6c0(0000) GS:ffff97cfa7133000(0000) knlGS:0000000000000000
> > [ 175.486046] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 175.486058] CR2: 00007f6b1092e888 CR3: 0000000101c3f000 CR4: 0000000000f50ef0
> > [ 175.486067] PKRU: 55555554
> > [ 175.486072] Call Trace:
> > [ 175.486081] <TASK>
> > [ 175.486092] ? smu_cmn_send_smc_msg_with_param+0xc0/0x360 [amdgpu]
> > [ 175.486102] amdgpu_bo_create_kernel+0x15/0x70 [amdgpu]
> > [ 175.486110] isp_kernel_buffer_alloc+0x56/0xa0 [amdgpu]
> > [ 175.486118] isp4if_gpu_mem_alloc.isra.0+0x45/0x70 [amd_capture]
> > [ 175.486126] isp4if_start+0x3a/0x320 [amd_capture]
> > [ 175.486141] isp4sd_set_power+0x96/0x1e0 [amd_capture]
> > [ 175.486148] pipeline_pm_power_one+0xf2/0x110 [videodev]
> > [ 175.486155] pipeline_pm_power+0x51/0x90 [videodev]
> > [ 175.486161] v4l2_pipeline_pm_use+0x3b/0x60 [videodev]
> > [ 175.486169] isp4vid_qops_start_streaming+0x22/0x140 [amd_capture]
> > [ 175.486176] ? isp4vid_qops_buffer_queue+0xb1/0x140 [amd_capture]
> > [ 175.486185] vb2_start_streaming+0x79/0x140 [videobuf2_common]
> > [ 175.486192] vb2_core_qbuf+0x3b5/0x480 [videobuf2_common]
> > [ 175.486200] vb2_qbuf+0x98/0x100 [videobuf2_v4l2]
> > [ 175.486208] __video_do_ioctl+0x480/0x4b0 [videodev]
> > [ 175.486219] video_usercopy+0x1e5/0x760 [videodev]
> > [ 175.486226] ? v4l_s_output+0x50/0x50 [videodev]
> > [ 175.486237] v4l2_ioctl+0x45/0x50 [videodev]
> > [ 175.486245] __x64_sys_ioctl+0x77/0xc0
> > [ 175.486251] do_syscall_64+0x48/0xbf0
> > [ 175.486260] entry_SYSCALL_64_after_hwframe+0x50/0x58
> > [ 175.486268] RIP: 0033:0x7fb03371674d
> > [ 175.486275] Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00
> > [ 175.486282] RSP: 002b:00007faf60ffc9d0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > [ 175.486292] RAX: ffffffffffffffda RBX: 00007fafb40050b0 RCX: 00007fb03371674d
> > [ 175.486301] RDX: 00007faf60ffca70 RSI: 00000000c058560f RDI: 000000000000002c
> > [ 175.486306] RBP: 00007faf60ffca20 R08: 13455f273d2513b9 R09: 0000000000000210
> > [ 175.486313] R10: 0000000000000215 R11: 0000000000000246 R12: 00007faf9801c4b0
> > [ 175.486318] R13: 0000000000000001 R14: 00007faf60ffcad0 R15: 0000000000000001
> > [ 175.486324] </TASK>
> > [ 175.486330] Modules linked in: ccm hid_sensor_prox hid_sensor_gyro_3d hid_sensor_trigger industrialio_triggered_buffer kfifo_buf hid_sensor_iio_common industrialio hid_sensor_hub rfcomm snd_seq_dummy snd_hrtimer snd_seq snd_seq_device amd_capture videobuf2_memops videobuf2_v4l2 videobuf2_common videodev mc pinctrl_amdisp i2c_designware_amdisp uhid cmac algif_hash algif_skcipher af_alg bnep uinput nls_iso8859_1 vfat fat snd_acp_legacy_mach snd_acp_mach snd_soc_nau8821 snd_acp3x_rn snd_acp70 snd_acp_i2s snd_acp_pdm joydev snd_soc_dmic snd_acp_pcm mousedev intel_rapl_msr snd_sof_amd_acp70 snd_sof_amd_acp63 snd_hda_scodec_cs35l56_spi intel_rapl_common snd_ctl_led snd_sof_amd_vangogh snd_sof_amd_rembrandt snd_hda_codec_alc269 snd_sof_amd_renoir snd_hda_scodec_component snd_sof_amd_acp snd_hda_codec_realtek_lib snd_sof_pci snd_sof_xtensa_dsp snd_hda_codec_generic snd_sof snd_sof_utils snd_pci_ps snd_soc_acpi_amd_match amdgpu snd_amd_sdw_acpi snd_hda_codec_atihdmi soundwire_amd soundwire_generic_allocation snd_hda_codec_hdmi
> > [ 175.486373] soundwire_bus snd_soc_sdca snd_soc_core snd_compress snd_hda_intel ac97_bus snd_pcm_dmaengine mt7925e drm_panel_backlight_quirks amdxcp snd_hda_codec snd_rpl_pci_acp6x mt7925_common btusb drm_buddy cdc_mbim mt792x_lib snd_acp_pci cdc_wdm btrtl drm_exec snd_hda_core snd_amd_acpi_mach mt76_connac_lib snd_hda_scodec_cs35l56_i2c btintel snd_acp_legacy_common drm_suballoc_helper cdc_ncm snd_intel_dspcfg mt76 snd_hda_scodec_cs35l56 snd_pci_acp6x cdc_ether drm_ttm_helper btbcm snd_intel_sdw_acpi snd_hda_cirrus_scodec snd_hwdep usbnet ttm snd_pci_acp5x btmtk snd_soc_cs35l56_shared ucsi_acpi kvm_amd mac80211 snd_pcm r8152 i2c_algo_bit snd_rn_pci_acp3x typec_ucsi snd_soc_cs_amp_lib libarc4 spd5118 bluetooth mii drm_display_helper snd_timer cs_dsp kvm typec snd_acp_config hp_wmi snd cfg80211 libphy amdxdna roles cec snd_soc_acpi ecdh_generic sp5100_tco hid_multitouch irqbypass sparse_keymap rfkill rapl mdio_bus video gpu_sched amd_pmf wmi_bmof snd_pci_acp3x soundcore amdtee i2c_hid_acpi serial_multi_instantiate
> > [ 175.486384] i2c_hid amd_sfh thunderbolt wireless_hotkey amd_pmc platform_profile wmi mac_hid i2c_piix4 i2c_smbus i2c_dev sg crypto_user loop nfnetlink ip_tables x_tables dm_crypt encrypted_keys trusted asn1_encoder tee dm_mod polyval_clmulni ghash_clmulni_intel aesni_intel nvme nvme_core nvme_keyring serio_raw ccp nvme_auth
> > [ 175.486394] CR2: 00007f6b1092e888
> > [ 175.486402] ---[ end trace 0000000000000000 ]---
> > [ 175.486409] RIP: 0010:amdgpu_bo_create_reserved+0xb1/0x1c0 [amdgpu]
> > [ 175.486416] Code: 8b 30 44 89 64 24 20 48 89 44 24 28 c7 44 24 30 01 00 00 00 c7 44 24 1c b8 02 00 00 c6 44 24 08 00 4d 85 f6 0f 84 a9 00 00 00 <49> 8b 86 a8 01 00 00 49 8b be 40 01 00 00 31 f6 48 89 04 24 e8 d6
> > [ 175.486422] RSP: 0018:ffff97b14e097ad0 EFLAGS: 00010202
> > [ 175.486429] RAX: 0000000000000021 RBX: ffff97b085af04d0 RCX: 0000000000000000
> > [ 175.486433] RDX: 0000000000008000 RSI: ffff97b14e097ae0 RDI: ffff97b14e097b20
> > [ 175.486439] RBP: ffff97b085af04c8 R08: ffff97b085af04d8 R09: ffff97b085af04c8
> > [ 175.486444] R10: 0000000000ffffff R11: ffff97b085af0560 R12: 0000000000000002
> > [ 175.486448] R13: ffff97b085af04d8 R14: 00007f6b1092e6e0 R15: ffff97b0a0f00000
> > [ 175.486455] FS: 00007faf60ffe6c0(0000) GS:ffff97cfa7133000(0000) knlGS:0000000000000000
> > [ 175.486460] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 175.486464] CR2: 00007f6b1092e888 CR3: 0000000101c3f000 CR4: 0000000000f50ef0
> > [ 175.486470] PKRU: 55555554
> >
> > Admittedly, it's my fault that ISP4 stopped zeroing the BO pointer argument
> > (&mem_info->mem_handle) passed to isp_kernel_buffer_alloc() [1]. But since this
> > issue slipped past Bin and presumably others who reviewed the code, it
> > highlights that isp_kernel_buffer_alloc() is not working as expected in this
> > respect, and the description for isp_kernel_buffer_alloc() reinforces this.
> >
> Thanks Sultan for suggesting this fix. Yes, its hard to believe that this
> slipped through until now.
>
> Instead of initializing *bo=NULL, I suggest ensuring *bo is actually NULL
> before calling amdgpu_bo_create_kernel().
>
> int isp_kernel_buffer_alloc(...)
> {
> ...
> if (WARN_ON(*bo))
> return -EINVAL;
> ...
> ret = amdgpu_bo_create_kernel(..)
> ...
> }
>
> This way the caller will get to know parameters passed are invalid and can
> take care of initializing the handles appropriately.
Hi Pratap,
I am opposed to this idea for multiple reasons:
1. *bo is an output parameter from isp_kernel_buffer_alloc(), so the input value
should not matter.
2. The only correct value for *bo is NULL when isp_kernel_buffer_alloc() passes
it to amdgpu_bo_create_kernel(). Since there is only one correct value, there
is no reason to burden callers of isp_kernel_buffer_alloc() with intializing
*bo to NULL.
3. This adds more code, another WARN_ON(), and another error case to
isp_kernel_buffer_alloc(). All of that can be eliminated entirely by just
initializing *bo to NULL in isp_kernel_buffer_alloc(), as I've done.
4. The reason *bo needs to be NULL is an implementation detail that is internal
to isp_kernel_buffer_alloc(), because amdgpu_bo_create_kernel() needs it to
be NULL in order to allocate a new buffer. isp_kernel_buffer_alloc() should
handle its own internal implementation details instead of punting the
responsibility onto callers.
Sultan
>
> Thanks,
> Pratap
>
> > > >
> > > > Ensure this by zeroing *bo right before the amdgpu_bo_create_kernel() call.
> > > >
> > > > Fixes: 55d42f616976 ("drm/amd/amdgpu: Add helper functions for isp buffers")
> > > > Signed-off-by: Sultan Alsawaf <sultan@...neltoast.com>
> > > > ---
> > > > drivers/gpu/drm/amd/amdgpu/amdgpu_isp.c | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_isp.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_isp.c
> > > > index 9cddbf50442a..37270c4dab8d 100644
> > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_isp.c
> > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_isp.c
> > > > @@ -280,6 +280,8 @@ int isp_kernel_buffer_alloc(struct device *dev, u64 size,
> > > > if (ret)
> > > > return ret;
> > > > + /* Ensure *bo is NULL so a new BO will be created */
> > > > + *bo = NULL;
> > > > ret = amdgpu_bo_create_kernel(adev,
> > > > size,
> > > > ISP_MC_ADDR_ALIGN,
> > >
> >
> > [1] https://lore.kernel.org/all/aNB0P18ytI1KopWI@sultan-box/
> >
> > Sultan
>
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