[PATCH v3 0/2] drm/i915/gem: Really move i915_gem_context.link under ref protection

[PATCH v3 0/2] drm/i915/gem: Really move i915_gem_context.link under ref protection

[Janusz Krzysztofik]

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=0x
1fffff ctx_id_mask=0x1fffff
[ 4070.574881] general protection fault, probably for non-canonical address 0xdead00000000
0100: 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 ]---

However, there is a risk of triggering kernel warning on contexts list not
empty at driver release time if we deleagate that task to a worker for
i915_gem_context_release_work(), unless that work is flushed first.
Unfortunately, it is not flushed on driver release.  Fix it.

Chris Wilson (1):
  drm/i915/gem: Really move i915_gem_context.link under ref protection

Janusz Krzysztofik (1):
  drm/i915/gem: Flush contexts on driver release

 drivers/gpu/drm/i915/gem/i915_gem_context.c | 8 ++++----
 drivers/gpu/drm/i915/i915_gem.c             | 3 ++-
 2 files changed, 6 insertions(+), 5 deletions(-)

-- 
2.25.1

[PATCH v3 1/2] drm/i915/gem: Flush contexts on driver release

[Janusz Krzysztofik]

Due to i915_perf assuming that it can use the i915_gem_context reference
to protect its i915->gem.contexts.list iteration, we need to defer removal
of the context from the list until last reference to the context is put.
However, there is a risk of triggering kernel warning on contexts list not
empty at driver release time if we deleagate that task to a worker for
i915_gem_context_release_work(), unless that work is flushed first.
Unfortunately, it is not flushed on driver release.  Fix it.

Instead of additionally calling flush_workqueue(), either directly or via
a new dedicated wrapper around it, replace last call to
i915_gem_drain_freed_objects() with existing i915_gem_drain_workqueue()
that performs both tasks.

Fixes: 75eefd82581f ("drm/i915: Release i915_gem_context from a worker")
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Cc: stable@kernel.org # v5.16+
---
 drivers/gpu/drm/i915/i915_gem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c8e14ed9c2a96..172c29a15f118 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1195,7 +1195,8 @@ void i915_gem_driver_release(struct drm_i915_private *dev_priv)
 
 	intel_uc_cleanup_firmwares(&to_gt(dev_priv)->uc);
 
-	i915_gem_drain_freed_objects(dev_priv);
+	/* Flush any outstanding work, including i915_gem_context.release_work. */
+	i915_gem_drain_workqueue(dev_priv);
 
 	drm_WARN_ON(&dev_priv->drm, !list_empty(&dev_priv->gem.contexts.list));
 }
-- 
2.25.1

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

[Janusz Krzysztofik]

From: Chris Wilson <chris@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@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@chris-wilson.co.uk>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: <stable@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);
-- 
2.25.1

Re: [Intel-gfx] [PATCH v3 1/2] drm/i915/gem: Flush contexts on driver release

[Gwan-gyeong Mun]

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

On 9/16/22 12:24 PM, Janusz Krzysztofik wrote:
> Due to i915_perf assuming that it can use the i915_gem_context reference
> to protect its i915->gem.contexts.list iteration, we need to defer removal
> of the context from the list until last reference to the context is put.
> However, there is a risk of triggering kernel warning on contexts list not
> empty at driver release time if we deleagate that task to a worker for
> i915_gem_context_release_work(), unless that work is flushed first.
> Unfortunately, it is not flushed on driver release.  Fix it.
> 
> Instead of additionally calling flush_workqueue(), either directly or via
> a new dedicated wrapper around it, replace last call to
> i915_gem_drain_freed_objects() with existing i915_gem_drain_workqueue()
> that performs both tasks.
> 
> Fixes: 75eefd82581f ("drm/i915: Release i915_gem_context from a worker")
> Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
> Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: stable@kernel.org # v5.16+
> ---
>   drivers/gpu/drm/i915/i915_gem.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c8e14ed9c2a96..172c29a15f118 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1195,7 +1195,8 @@ void i915_gem_driver_release(struct drm_i915_private *dev_priv)
>   
>   	intel_uc_cleanup_firmwares(&to_gt(dev_priv)->uc);
>   
> -	i915_gem_drain_freed_objects(dev_priv);
> +	/* Flush any outstanding work, including i915_gem_context.release_work. */
> +	i915_gem_drain_workqueue(dev_priv);
>   
>   	drm_WARN_ON(&dev_priv->drm, !list_empty(&dev_priv->gem.contexts.list));
>   }

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

[Gwan-gyeong Mun]

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

On 9/16/22 12:24 PM, Janusz Krzysztofik wrote:
> From: Chris Wilson <chris@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@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@chris-wilson.co.uk>
> Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
> Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: <stable@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);

Re: [PATCH v3 0/2] drm/i915/gem: Really move i915_gem_context.link under ref protection

[Andi Shyti]

Pushed, Thanks!

Andi

On Fri, Sep 16, 2022 at 11:24:01AM +0200, Janusz Krzysztofik wrote:
> 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=0x
> 1fffff ctx_id_mask=0x1fffff
> [ 4070.574881] general protection fault, probably for non-canonical address 0xdead00000000
> 0100: 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 ]---
> 
> However, there is a risk of triggering kernel warning on contexts list not
> empty at driver release time if we deleagate that task to a worker for
> i915_gem_context_release_work(), unless that work is flushed first.
> Unfortunately, it is not flushed on driver release.  Fix it.
> 
> Chris Wilson (1):
>   drm/i915/gem: Really move i915_gem_context.link under ref protection
> 
> Janusz Krzysztofik (1):
>   drm/i915/gem: Flush contexts on driver release
> 
>  drivers/gpu/drm/i915/gem/i915_gem_context.c | 8 ++++----
>  drivers/gpu/drm/i915/i915_gem.c             | 3 ++-
>  2 files changed, 6 insertions(+), 5 deletions(-)
> 
> -- 
> 2.25.1