[PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[daniele.ceraolospurio]

From: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>

While running some tests on the scheduler patches with rpm enabled I
came across a corruption in the ringbuffer, which was root-caused to
the GPU being suspended while commands were being emitted to the
ringbuffer. The access to memory was failing because the GPU needs to
be awake when accessing stolen memory (where my ringbuffer was located).
Since we have this constraint it looks like a sensible idea to check
that we hold a refcount when we access the rungbuffer.

v2: move the check from ring_begin to ringbuffer iomap time (Chris)
v3: update comment (Chris)

Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 6f5b511..133321a 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2119,6 +2119,9 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 			return ret;
 		}
 
+		/* Access through the GTT requires the device to be awake. */
+		assert_rpm_wakelock_held(dev_priv);
+
 		ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
 						    i915_gem_obj_ggtt_offset(obj), ringbuf->size);
 		if (ringbuf->virtual_start == NULL) {
-- 
1.9.1

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Re: [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Ville Syrjälä]

On Wed, Jan 27, 2016 at 03:43:49PM +0000, daniele.ceraolospurio@intel.com wrote:
> From: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> 
> While running some tests on the scheduler patches with rpm enabled I
> came across a corruption in the ringbuffer, which was root-caused to
> the GPU being suspended while commands were being emitted to the
> ringbuffer. The access to memory was failing because the GPU needs to
> be awake when accessing stolen memory (where my ringbuffer was located).
> Since we have this constraint it looks like a sensible idea to check
> that we hold a refcount when we access the rungbuffer.
> 
> v2: move the check from ring_begin to ringbuffer iomap time (Chris)
> v3: update comment (Chris)
> 
> Cc: John Harrison <John.C.Harrison@Intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 6f5b511..133321a 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -2119,6 +2119,9 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
>  			return ret;
>  		}
>  
> +		/* Access through the GTT requires the device to be awake. */
> +		assert_rpm_wakelock_held(dev_priv);
> +

Hmm. This function doesn't actually acces the ring buffer, so it's a bit
odd to see this here.

>  		ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
>  						    i915_gem_obj_ggtt_offset(obj), ringbuf->size);
>  		if (ringbuf->virtual_start == NULL) {
> -- 
> 1.9.1
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
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Re: [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Chris Wilson]

On Wed, Jan 27, 2016 at 03:43:49PM +0000, daniele.ceraolospurio@intel.com wrote:
> From: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> 
> While running some tests on the scheduler patches with rpm enabled I
> came across a corruption in the ringbuffer, which was root-caused to
> the GPU being suspended while commands were being emitted to the
> ringbuffer. The access to memory was failing because the GPU needs to
> be awake when accessing stolen memory (where my ringbuffer was located).
> Since we have this constraint it looks like a sensible idea to check
> that we hold a refcount when we access the rungbuffer.
> 
> v2: move the check from ring_begin to ringbuffer iomap time (Chris)
> v3: update comment (Chris)
> 
> Cc: John Harrison <John.C.Harrison@Intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>

That explains itself nicely, thanks.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

It also rings alarms bells for intel_fbdev.c
-Chris

-- 
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✓ Fi.CI.BAT: success for drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem (rev2)

[Patchwork]

== Summary ==

Built on 430706bace599ea1a908b9a7c6b7ea17535fe17f drm-intel-nightly: 2016y-01m-27d-16h-33m-06s UTC integration manifest

Test kms_pipe_crc_basic:
        Subgroup read-crc-pipe-b:
                dmesg-warn -> PASS       (ilk-hp8440p)

bdw-nuci7        total:141  pass:132  dwarn:0   dfail:0   fail:0   skip:9  
bsw-nuc-2        total:144  pass:120  dwarn:0   dfail:0   fail:0   skip:24 
byt-nuc          total:144  pass:129  dwarn:0   dfail:0   fail:0   skip:15 
hsw-brixbox      total:144  pass:137  dwarn:0   dfail:0   fail:0   skip:7  
hsw-gt2          total:144  pass:140  dwarn:0   dfail:0   fail:0   skip:4  
ilk-hp8440p      total:144  pass:105  dwarn:0   dfail:0   fail:1   skip:38 
ivb-t430s        total:144  pass:138  dwarn:0   dfail:0   fail:0   skip:6  
skl-i5k-2        total:144  pass:135  dwarn:1   dfail:0   fail:0   skip:8  
snb-dellxps      total:144  pass:130  dwarn:0   dfail:0   fail:0   skip:14 
snb-x220t        total:144  pass:130  dwarn:0   dfail:0   fail:1   skip:13 

Results at /archive/results/CI_IGT_test/Patchwork_1277/

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Re: [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Daniele Ceraolo Spurio]

On 27/01/16 16:39, Ville Syrjälä wrote:
> On Wed, Jan 27, 2016 at 03:43:49PM +0000,daniele.ceraolospurio@intel.com  wrote:
>> From: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
>>
>> While running some tests on the scheduler patches with rpm enabled I
>> came across a corruption in the ringbuffer, which was root-caused to
>> the GPU being suspended while commands were being emitted to the
>> ringbuffer. The access to memory was failing because the GPU needs to
>> be awake when accessing stolen memory (where my ringbuffer was located).
>> Since we have this constraint it looks like a sensible idea to check
>> that we hold a refcount when we access the rungbuffer.
>>
>> v2: move the check from ring_begin to ringbuffer iomap time (Chris)
>> v3: update comment (Chris)
>>
>> Cc: John Harrison<John.C.Harrison@Intel.com>
>> Cc: Chris Wilson<chris@chris-wilson.co.uk>
>> Signed-off-by: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> index 6f5b511..133321a 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> @@ -2119,6 +2119,9 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
>>   			return ret;
>>   		}
>>   
>> +		/* Access through the GTT requires the device to be awake. */
>> +		assert_rpm_wakelock_held(dev_priv);
>> +
> Hmm. This function doesn't actually acces the ring buffer, so it's a bit
> odd to see this here.

I had it inring_begin initially, but Chris suggested moving it here 
because we pin the ringbuffer before accessing it. Do you have a 
different place in mind for where this should be added or would you be 
happy with a simple comment update?

Thanks,
Daniele

>>   		ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
>>   						    i915_gem_obj_ggtt_offset(obj), ringbuf->size);
>>   		if (ringbuf->virtual_start == NULL) {
>> -- 
>> 1.9.1
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

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Re: [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Chris Wilson]

On Thu, Jan 28, 2016 at 10:55:16AM +0000, Daniele Ceraolo Spurio wrote:
> 
> 
> On 27/01/16 16:39, Ville Syrjälä wrote:
> >On Wed, Jan 27, 2016 at 03:43:49PM +0000,daniele.ceraolospurio@intel.com  wrote:
> >>From: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
> >>
> >>While running some tests on the scheduler patches with rpm enabled I
> >>came across a corruption in the ringbuffer, which was root-caused to
> >>the GPU being suspended while commands were being emitted to the
> >>ringbuffer. The access to memory was failing because the GPU needs to
> >>be awake when accessing stolen memory (where my ringbuffer was located).
> >>Since we have this constraint it looks like a sensible idea to check
> >>that we hold a refcount when we access the rungbuffer.
> >>
> >>v2: move the check from ring_begin to ringbuffer iomap time (Chris)
> >>v3: update comment (Chris)
> >>
> >>Cc: John Harrison<John.C.Harrison@Intel.com>
> >>Cc: Chris Wilson<chris@chris-wilson.co.uk>
> >>Signed-off-by: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
> >>---
> >>  drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>index 6f5b511..133321a 100644
> >>--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >>@@ -2119,6 +2119,9 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
> >>  			return ret;
> >>  		}
> >>+		/* Access through the GTT requires the device to be awake. */
> >>+		assert_rpm_wakelock_held(dev_priv);
> >>+
> >Hmm. This function doesn't actually acces the ring buffer, so it's a bit
> >odd to see this here.
> 
> I had it inring_begin initially, but Chris suggested moving it here
> because we pin the ringbuffer before accessing it. Do you have a
> different place in mind for where this should be added or would you
> be happy with a simple comment update?

This function we call in order to acquire access to the ring iomap for
the request. At the beginning of the request, we should be pinning
everything we need to build the request. If writing through the GTT we
should be ensuring that the device is also awake. The oddity is that
this is not yet explicit and the asymmetry still exists between
legacy/execlists.
-Chris

-- 
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Re: [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Ville Syrjälä]

On Thu, Jan 28, 2016 at 11:45:24AM +0000, Chris Wilson wrote:
> On Thu, Jan 28, 2016 at 10:55:16AM +0000, Daniele Ceraolo Spurio wrote:
> > 
> > 
> > On 27/01/16 16:39, Ville Syrjälä wrote:
> > >On Wed, Jan 27, 2016 at 03:43:49PM +0000,daniele.ceraolospurio@intel.com  wrote:
> > >>From: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
> > >>
> > >>While running some tests on the scheduler patches with rpm enabled I
> > >>came across a corruption in the ringbuffer, which was root-caused to
> > >>the GPU being suspended while commands were being emitted to the
> > >>ringbuffer. The access to memory was failing because the GPU needs to
> > >>be awake when accessing stolen memory (where my ringbuffer was located).
> > >>Since we have this constraint it looks like a sensible idea to check
> > >>that we hold a refcount when we access the rungbuffer.
> > >>
> > >>v2: move the check from ring_begin to ringbuffer iomap time (Chris)
> > >>v3: update comment (Chris)
> > >>
> > >>Cc: John Harrison<John.C.Harrison@Intel.com>
> > >>Cc: Chris Wilson<chris@chris-wilson.co.uk>
> > >>Signed-off-by: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
> > >>---
> > >>  drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
> > >>  1 file changed, 3 insertions(+)
> > >>
> > >>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > >>index 6f5b511..133321a 100644
> > >>--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > >>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > >>@@ -2119,6 +2119,9 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
> > >>  			return ret;
> > >>  		}
> > >>+		/* Access through the GTT requires the device to be awake. */
> > >>+		assert_rpm_wakelock_held(dev_priv);
> > >>+
> > >Hmm. This function doesn't actually acces the ring buffer, so it's a bit
> > >odd to see this here.
> > 
> > I had it inring_begin initially, but Chris suggested moving it here
> > because we pin the ringbuffer before accessing it. Do you have a
> > different place in mind for where this should be added or would you
> > be happy with a simple comment update?
> 
> This function we call in order to acquire access to the ring iomap for
> the request. At the beginning of the request, we should be pinning
> everything we need to build the request. If writing through the GTT we
> should be ensuring that the device is also awake. The oddity is that
> this is not yet explicit and the asymmetry still exists between
> legacy/execlists.

Yeah, with ringbuffer mode this gets executed exactly once, so more or
less useless at the moment. With execlists I suppose it might catch
something on CHV/BXT.

-- 
Ville Syrjälä
Intel OTC
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Re: [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Chris Wilson]

On Thu, Jan 28, 2016 at 02:09:37PM +0200, Ville Syrjälä wrote:
> On Thu, Jan 28, 2016 at 11:45:24AM +0000, Chris Wilson wrote:
> > On Thu, Jan 28, 2016 at 10:55:16AM +0000, Daniele Ceraolo Spurio wrote:
> > > 
> > > 
> > > On 27/01/16 16:39, Ville Syrjälä wrote:
> > > >On Wed, Jan 27, 2016 at 03:43:49PM +0000,daniele.ceraolospurio@intel.com  wrote:
> > > >>From: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
> > > >>
> > > >>While running some tests on the scheduler patches with rpm enabled I
> > > >>came across a corruption in the ringbuffer, which was root-caused to
> > > >>the GPU being suspended while commands were being emitted to the
> > > >>ringbuffer. The access to memory was failing because the GPU needs to
> > > >>be awake when accessing stolen memory (where my ringbuffer was located).
> > > >>Since we have this constraint it looks like a sensible idea to check
> > > >>that we hold a refcount when we access the rungbuffer.
> > > >>
> > > >>v2: move the check from ring_begin to ringbuffer iomap time (Chris)
> > > >>v3: update comment (Chris)
> > > >>
> > > >>Cc: John Harrison<John.C.Harrison@Intel.com>
> > > >>Cc: Chris Wilson<chris@chris-wilson.co.uk>
> > > >>Signed-off-by: Daniele Ceraolo Spurio<daniele.ceraolospurio@intel.com>
> > > >>---
> > > >>  drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
> > > >>  1 file changed, 3 insertions(+)
> > > >>
> > > >>diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > > >>index 6f5b511..133321a 100644
> > > >>--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> > > >>+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> > > >>@@ -2119,6 +2119,9 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
> > > >>  			return ret;
> > > >>  		}
> > > >>+		/* Access through the GTT requires the device to be awake. */
> > > >>+		assert_rpm_wakelock_held(dev_priv);
> > > >>+
> > > >Hmm. This function doesn't actually acces the ring buffer, so it's a bit
> > > >odd to see this here.
> > > 
> > > I had it inring_begin initially, but Chris suggested moving it here
> > > because we pin the ringbuffer before accessing it. Do you have a
> > > different place in mind for where this should be added or would you
> > > be happy with a simple comment update?
> > 
> > This function we call in order to acquire access to the ring iomap for
> > the request. At the beginning of the request, we should be pinning
> > everything we need to build the request. If writing through the GTT we
> > should be ensuring that the device is also awake. The oddity is that
> > this is not yet explicit and the asymmetry still exists between
> > legacy/execlists.
> 
> Yeah, with ringbuffer mode this gets executed exactly once, so more or
> less useless at the moment. With execlists I suppose it might catch
> something on CHV/BXT.

It shouldn't. We hold the wakeref for execbuf request construction, and
that is more or less the only time we create a request in execlists.
(Although it doesn't have to be that way!)
-Chris

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✓ Fi.CI.BAT: success for drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem (rev2)

[Patchwork]

== Summary ==

Series 2878v2 drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem
http://patchwork.freedesktop.org/api/1.0/series/2878/revisions/2/mbox/

Test gem_exec_basic:
        Subgroup basic-bsd1:
                pass       -> SKIP       (bsw-nuc-2)
                pass       -> SKIP       (hsw-gt2)
                pass       -> SKIP       (skl-i5k-2)
                pass       -> SKIP       (ivb-t430s)
                pass       -> SKIP       (bdw-ultra)
                pass       -> SKIP       (byt-nuc)
                pass       -> SKIP       (snb-x220t)
                pass       -> SKIP       (snb-dellxps)
                pass       -> SKIP       (hsw-brixbox)
                pass       -> SKIP       (ilk-hp8440p)
        Subgroup basic-bsd2:
                pass       -> SKIP       (bsw-nuc-2)
                pass       -> SKIP       (hsw-gt2)
                pass       -> SKIP       (skl-i5k-2)
                pass       -> SKIP       (ivb-t430s)
                pass       -> SKIP       (bdw-ultra)
                pass       -> SKIP       (byt-nuc)
                pass       -> SKIP       (snb-x220t)
                pass       -> SKIP       (snb-dellxps)
                pass       -> SKIP       (hsw-brixbox)
                pass       -> SKIP       (ilk-hp8440p)
Test gem_ringfill:
        Subgroup basic-default:
                fail       -> PASS       (ilk-hp8440p)
Test gem_storedw_loop:
        Subgroup basic-bsd1:
                pass       -> SKIP       (bsw-nuc-2)
                pass       -> SKIP       (skl-i5k-2)
                pass       -> SKIP       (hsw-gt2)
                pass       -> SKIP       (bdw-ultra)
                pass       -> SKIP       (ivb-t430s)
                pass       -> SKIP       (byt-nuc)
                pass       -> SKIP       (hsw-brixbox)
        Subgroup basic-bsd2:
                pass       -> SKIP       (bsw-nuc-2)
                pass       -> SKIP       (skl-i5k-2)
                pass       -> SKIP       (hsw-gt2)
                pass       -> SKIP       (bdw-ultra)
                pass       -> SKIP       (ivb-t430s)
                pass       -> SKIP       (byt-nuc)
                pass       -> SKIP       (hsw-brixbox)
Test gem_sync:
        Subgroup basic-bsd1:
                pass       -> SKIP       (bsw-nuc-2)
                pass       -> SKIP       (hsw-gt2)
                pass       -> SKIP       (skl-i5k-2)
                pass       -> SKIP       (ivb-t430s)
                pass       -> SKIP       (bdw-ultra)
                pass       -> SKIP       (byt-nuc)
                pass       -> SKIP       (snb-x220t)
                pass       -> SKIP       (snb-dellxps)
                pass       -> SKIP       (hsw-brixbox)
                pass       -> SKIP       (ilk-hp8440p)
        Subgroup basic-bsd2:
                pass       -> SKIP       (bsw-nuc-2)
                pass       -> SKIP       (hsw-gt2)
                pass       -> SKIP       (skl-i5k-2)
                pass       -> SKIP       (ivb-t430s)
                pass       -> SKIP       (bdw-ultra)
                pass       -> SKIP       (byt-nuc)
                pass       -> SKIP       (snb-x220t)
                pass       -> SKIP       (snb-dellxps)
                pass       -> SKIP       (hsw-brixbox)
                pass       -> SKIP       (ilk-hp8440p)
Test kms_flip:
        Subgroup basic-flip-vs-dpms:
                pass       -> DMESG-WARN (ilk-hp8440p) UNSTABLE

bdw-nuci7        total:156  pass:147  dwarn:0   dfail:0   fail:0   skip:9  
bdw-ultra        total:159  pass:147  dwarn:0   dfail:0   fail:0   skip:12 
bsw-nuc-2        total:159  pass:129  dwarn:0   dfail:0   fail:0   skip:30 
byt-nuc          total:159  pass:136  dwarn:0   dfail:0   fail:0   skip:23 
hsw-brixbox      total:159  pass:146  dwarn:0   dfail:0   fail:0   skip:13 
hsw-gt2          total:159  pass:149  dwarn:0   dfail:0   fail:0   skip:10 
ilk-hp8440p      total:159  pass:110  dwarn:1   dfail:0   fail:0   skip:48 
ivb-t430s        total:159  pass:145  dwarn:0   dfail:0   fail:0   skip:14 
skl-i5k-2        total:159  pass:144  dwarn:1   dfail:0   fail:0   skip:14 
snb-dellxps      total:159  pass:137  dwarn:0   dfail:0   fail:0   skip:22 
snb-x220t        total:159  pass:137  dwarn:0   dfail:0   fail:1   skip:21 

Results at /archive/results/CI_IGT_test/Patchwork_1305/

b3f8ad64bc71f6236f05c2e9f4ad49a61745869a drm-intel-nightly: 2016y-01m-28d-10h-26m-23s UTC integration manifest
394a37654e14e8c2e309c26fb852fb8613c61050 drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

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Re: [PATCH v3] drm/i915: check that rpm ref is held when accessing ringbuf in stolen mem

[Daniel Vetter]

On Wed, Jan 27, 2016 at 04:44:37PM +0000, Chris Wilson wrote:
> On Wed, Jan 27, 2016 at 03:43:49PM +0000, daniele.ceraolospurio@intel.com wrote:
> > From: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> > 
> > While running some tests on the scheduler patches with rpm enabled I
> > came across a corruption in the ringbuffer, which was root-caused to
> > the GPU being suspended while commands were being emitted to the
> > ringbuffer. The access to memory was failing because the GPU needs to
> > be awake when accessing stolen memory (where my ringbuffer was located).
> > Since we have this constraint it looks like a sensible idea to check
> > that we hold a refcount when we access the rungbuffer.
> > 
> > v2: move the check from ring_begin to ringbuffer iomap time (Chris)
> > v3: update comment (Chris)
> > 
> > Cc: John Harrison <John.C.Harrison@Intel.com>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> 
> That explains itself nicely, thanks.
> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

Queued for -next, thanks for the patch.

> It also rings alarms bells for intel_fbdev.c

Oops, indeed. Might explain why we sometimes just die? And fundamentally
it's unfixable (without a shadow fb) since we can't intercept mmaps on
fbdev. But maybe we need to do that (and use the damage tracking that's
already there in 3 copies in various drivers for uploading).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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