[Intel-gfx] [PATCH v3 2/2] drm/i915/gem: Really move i915_gem_context.link under ref protection

Fri Sep 16 12:07:41 UTC 2022

Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>

On 9/16/22 12:24 PM, Janusz Krzysztofik wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
> 
> i915_perf assumes that it can use the i915_gem_context reference to
> protect its i915->gem.contexts.list iteration. However, this requires
> that we do not remove the context from the list until after we drop the
> final reference and release the struct. If, as currently, we remove the
> context from the list during context_close(), the link.next pointer may
> be poisoned while we are holding the context reference and cause a GPF:
> 
> [ 4070.573157] i915 0000:00:02.0: [drm:i915_perf_open_ioctl [i915]] filtering on ctx_id=0x1fffff ctx_id_mask=0x1fffff
> [ 4070.574881] general protection fault, probably for non-canonical address 0xdead000000000100: 0000 [#1] PREEMPT SMP
> [ 4070.574897] CPU: 1 PID: 284392 Comm: amd_performance Tainted: G            E     5.17.9 #180
> [ 4070.574903] Hardware name: Intel Corporation NUC7i5BNK/NUC7i5BNB, BIOS BNKBL357.86A.0052.2017.0918.1346 09/18/2017
> [ 4070.574907] RIP: 0010:oa_configure_all_contexts.isra.0+0x222/0x350 [i915]
> [ 4070.574982] Code: 08 e8 32 6e 10 e1 4d 8b 6d 50 b8 ff ff ff ff 49 83 ed 50 f0 41 0f c1 04 24 83 f8 01 0f 84 e3 00 00 00 85 c0 0f 8e fa 00 00 00 <49> 8b 45 50 48 8d 70 b0 49 8d 45 50 48 39 44 24 10 0f 85 34 fe ff
> [ 4070.574990] RSP: 0018:ffffc90002077b78 EFLAGS: 00010202
> [ 4070.574995] RAX: 0000000000000002 RBX: 0000000000000002 RCX: 0000000000000000
> [ 4070.575000] RDX: 0000000000000001 RSI: ffffc90002077b20 RDI: ffff88810ddc7c68
> [ 4070.575004] RBP: 0000000000000001 R08: ffff888103242648 R09: fffffffffffffffc
> [ 4070.575008] R10: ffffffff82c50bc0 R11: 0000000000025c80 R12: ffff888101bf1860
> [ 4070.575012] R13: dead0000000000b0 R14: ffffc90002077c04 R15: ffff88810be5cabc
> [ 4070.575016] FS:  00007f1ed50c0780(0000) GS:ffff88885ec80000(0000) knlGS:0000000000000000
> [ 4070.575021] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 4070.575025] CR2: 00007f1ed5590280 CR3: 000000010ef6f005 CR4: 00000000003706e0
> [ 4070.575029] Call Trace:
> [ 4070.575033]  <TASK>
> [ 4070.575037]  lrc_configure_all_contexts+0x13e/0x150 [i915]
> [ 4070.575103]  gen8_enable_metric_set+0x4d/0x90 [i915]
> [ 4070.575164]  i915_perf_open_ioctl+0xbc0/0x1500 [i915]
> [ 4070.575224]  ? asm_common_interrupt+0x1e/0x40
> [ 4070.575232]  ? i915_oa_init_reg_state+0x110/0x110 [i915]
> [ 4070.575290]  drm_ioctl_kernel+0x85/0x110
> [ 4070.575296]  ? update_load_avg+0x5f/0x5e0
> [ 4070.575302]  drm_ioctl+0x1d3/0x370
> [ 4070.575307]  ? i915_oa_init_reg_state+0x110/0x110 [i915]
> [ 4070.575382]  ? gen8_gt_irq_handler+0x46/0x130 [i915]
> [ 4070.575445]  __x64_sys_ioctl+0x3c4/0x8d0
> [ 4070.575451]  ? __do_softirq+0xaa/0x1d2
> [ 4070.575456]  do_syscall_64+0x35/0x80
> [ 4070.575461]  entry_SYSCALL_64_after_hwframe+0x44/0xae
> [ 4070.575467] RIP: 0033:0x7f1ed5c10397
> [ 4070.575471] Code: 3c 1c e8 1c ff ff ff 85 c0 79 87 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c c3 66 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a9 da 0d 00 f7 d8 64 89 01 48
> [ 4070.575478] RSP: 002b:00007ffd65c8d7a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> [ 4070.575484] RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007f1ed5c10397
> [ 4070.575488] RDX: 00007ffd65c8d7c0 RSI: 0000000040106476 RDI: 0000000000000006
> [ 4070.575492] RBP: 00005620972f9c60 R08: 000000000000000a R09: 0000000000000005
> [ 4070.575496] R10: 000000000000000d R11: 0000000000000246 R12: 000000000000000a
> [ 4070.575500] R13: 000000000000000d R14: 0000000000000000 R15: 00007ffd65c8d7c0
> [ 4070.575505]  </TASK>
> [ 4070.575507] Modules linked in: nls_ascii(E) nls_cp437(E) vfat(E) fat(E) i915(E) x86_pkg_temp_thermal(E) intel_powerclamp(E) crct10dif_pclmul(E) crc32_pclmul(E) crc32c_intel(E) aesni_intel(E) crypto_simd(E) intel_gtt(E) cryptd(E) ttm(E) rapl(E) intel_cstate(E) drm_kms_helper(E) cfbfillrect(E) syscopyarea(E) cfbimgblt(E) intel_uncore(E) sysfillrect(E) mei_me(E) sysimgblt(E) i2c_i801(E) fb_sys_fops(E) mei(E) intel_pch_thermal(E) i2c_smbus(E) cfbcopyarea(E) video(E) button(E) efivarfs(E) autofs4(E)
> [ 4070.575549] ---[ end trace 0000000000000000 ]---
> 
> v3: fix incorrect syntax of spin_lock() replacing spin_lock_irqsave()
> 
> v2: irqsave not required in a worker, neither conversion to irq safe
>      elsewhere (Tvrtko),
>    - perf: it's safe to call gen8_configure_context() even if context has
>      been closed, no need to check,
>    - drop unrelated cleanup (Andi, Tvrtko)
> 
> Reported-by: Mark Janes <mark.janes at intel.com>
> Closes: https://gitlab.freedesktop.org/drm/intel/issues/6222
> References: a4e7ccdac38e ("drm/i915: Move context management under GEM")
> Fixes: f8246cf4d9a9 ("drm/i915/gem: Drop free_work for GEM contexts")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Reviewed-by: Andi Shyti <andi.shyti at linux.intel.com>
> Signed-off-by: Andi Shyti <andi.shyti at linux.intel.com>
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: <stable at vger.kernel.org> # v5.12+
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_context.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index dabdfe09f5e51..0bcde53c50c61 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -1269,6 +1269,10 @@ static void i915_gem_context_release_work(struct work_struct *work)
>   	trace_i915_context_free(ctx);
>   	GEM_BUG_ON(!i915_gem_context_is_closed(ctx));
>   
> +	spin_lock(&ctx->i915->gem.contexts.lock);
> +	list_del(&ctx->link);
> +	spin_unlock(&ctx->i915->gem.contexts.lock);
> +
>   	if (ctx->syncobj)
>   		drm_syncobj_put(ctx->syncobj);
>   
> @@ -1521,10 +1525,6 @@ static void context_close(struct i915_gem_context *ctx)
>   
>   	ctx->file_priv = ERR_PTR(-EBADF);
>   
> -	spin_lock(&ctx->i915->gem.contexts.lock);
> -	list_del(&ctx->link);
> -	spin_unlock(&ctx->i915->gem.contexts.lock);
> -
>   	client = ctx->client;
>   	if (client) {
>   		spin_lock(&client->ctx_lock);