* [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
@ 2018-04-10 17:05 Takashi Iwai
2018-04-10 17:06 ` Christoph Hellwig
0 siblings, 1 reply; 12+ messages in thread
From: Takashi Iwai @ 2018-04-10 17:05 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Christian König, Konrad Rzeszutek Wilk, iommu, linux-kernel
The code refactoring by commit 0176adb00406 ("swiotlb: refactor
coherent buffer allocation") made swiotlb_alloc_buffer() almost always
failing due to a thinko: namely, the function evaluates the
dma_coherent_ok() call incorrectly and dealing as if it's invalid.
This ends up with weird errors like iwlwifi probe failure or amdgpu
screen flickering.
This patch corrects the logic error.
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088658
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088902
Fixes: 0176adb00406 ("swiotlb: refactor coherent buffer allocation")
Cc: <stable@vger.kernel.org> # v4.16+
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
lib/swiotlb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 47aeb04c1997..de7cc540450f 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -719,7 +719,7 @@ swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
goto out_warn;
*dma_handle = __phys_to_dma(dev, phys_addr);
- if (dma_coherent_ok(dev, *dma_handle, size))
+ if (!dma_coherent_ok(dev, *dma_handle, size))
goto out_unmap;
memset(phys_to_virt(phys_addr), 0, size);
--
2.16.3
^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-10 17:05 [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures Takashi Iwai
@ 2018-04-10 17:06 ` Christoph Hellwig
2018-04-10 17:07 ` Takashi Iwai
0 siblings, 1 reply; 12+ messages in thread
From: Christoph Hellwig @ 2018-04-10 17:06 UTC (permalink / raw)
To: Takashi Iwai
Cc: Christoph Hellwig, Christian König, Konrad Rzeszutek Wilk,
iommu, linux-kernel
On Tue, Apr 10, 2018 at 07:05:13PM +0200, Takashi Iwai wrote:
> The code refactoring by commit 0176adb00406 ("swiotlb: refactor
> coherent buffer allocation") made swiotlb_alloc_buffer() almost always
> failing due to a thinko: namely, the function evaluates the
> dma_coherent_ok() call incorrectly and dealing as if it's invalid.
> This ends up with weird errors like iwlwifi probe failure or amdgpu
> screen flickering.
>
> This patch corrects the logic error.
This looks ok, although even hitting this code is a bad sign. Do you
know why the previous dma_direct_alloc didn't succeed?
>
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088658
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088902
> Fixes: 0176adb00406 ("swiotlb: refactor coherent buffer allocation")
> Cc: <stable@vger.kernel.org> # v4.16+
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
> lib/swiotlb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index 47aeb04c1997..de7cc540450f 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -719,7 +719,7 @@ swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
> goto out_warn;
>
> *dma_handle = __phys_to_dma(dev, phys_addr);
> - if (dma_coherent_ok(dev, *dma_handle, size))
> + if (!dma_coherent_ok(dev, *dma_handle, size))
> goto out_unmap;
>
> memset(phys_to_virt(phys_addr), 0, size);
> --
> 2.16.3
---end quoted text---
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-10 17:06 ` Christoph Hellwig
@ 2018-04-10 17:07 ` Takashi Iwai
2018-04-10 17:50 ` Robin Murphy
0 siblings, 1 reply; 12+ messages in thread
From: Takashi Iwai @ 2018-04-10 17:07 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Christian König, Konrad Rzeszutek Wilk, iommu, linux-kernel
On Tue, 10 Apr 2018 19:06:15 +0200,
Christoph Hellwig wrote:
>
> On Tue, Apr 10, 2018 at 07:05:13PM +0200, Takashi Iwai wrote:
> > The code refactoring by commit 0176adb00406 ("swiotlb: refactor
> > coherent buffer allocation") made swiotlb_alloc_buffer() almost always
> > failing due to a thinko: namely, the function evaluates the
> > dma_coherent_ok() call incorrectly and dealing as if it's invalid.
> > This ends up with weird errors like iwlwifi probe failure or amdgpu
> > screen flickering.
> >
> > This patch corrects the logic error.
>
> This looks ok, although even hitting this code is a bad sign. Do you
> know why the previous dma_direct_alloc didn't succeed?
That I have no idea, sorry. I just figured out the regression just
from the dmesg output of 4.16 kernel in bugzilla reports.
Could you take a look at the bugzilla reports there?
thanks,
Takashi
> > Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088658
> > Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088902
> > Fixes: 0176adb00406 ("swiotlb: refactor coherent buffer allocation")
> > Cc: <stable@vger.kernel.org> # v4.16+
> > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > ---
> > lib/swiotlb.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> > index 47aeb04c1997..de7cc540450f 100644
> > --- a/lib/swiotlb.c
> > +++ b/lib/swiotlb.c
> > @@ -719,7 +719,7 @@ swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
> > goto out_warn;
> >
> > *dma_handle = __phys_to_dma(dev, phys_addr);
> > - if (dma_coherent_ok(dev, *dma_handle, size))
> > + if (!dma_coherent_ok(dev, *dma_handle, size))
> > goto out_unmap;
> >
> > memset(phys_to_virt(phys_addr), 0, size);
> > --
> > 2.16.3
> ---end quoted text---
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-10 17:07 ` Takashi Iwai
@ 2018-04-10 17:50 ` Robin Murphy
2018-04-10 18:10 ` Christoph Hellwig
0 siblings, 1 reply; 12+ messages in thread
From: Robin Murphy @ 2018-04-10 17:50 UTC (permalink / raw)
To: Takashi Iwai, Christoph Hellwig
Cc: linux-kernel, iommu, Christian König, Konrad Rzeszutek Wilk
On 10/04/18 18:07, Takashi Iwai wrote:
> On Tue, 10 Apr 2018 19:06:15 +0200,
> Christoph Hellwig wrote:
>>
>> On Tue, Apr 10, 2018 at 07:05:13PM +0200, Takashi Iwai wrote:
>>> The code refactoring by commit 0176adb00406 ("swiotlb: refactor
>>> coherent buffer allocation") made swiotlb_alloc_buffer() almost always
>>> failing due to a thinko: namely, the function evaluates the
>>> dma_coherent_ok() call incorrectly and dealing as if it's invalid.
>>> This ends up with weird errors like iwlwifi probe failure or amdgpu
>>> screen flickering.
>>>
>>> This patch corrects the logic error.
>>
>> This looks ok, although even hitting this code is a bad sign. Do you
>> know why the previous dma_direct_alloc didn't succeed?
>
> That I have no idea, sorry. I just figured out the regression just
> from the dmesg output of 4.16 kernel in bugzilla reports.
> Could you take a look at the bugzilla reports there?
In the first one, the machine appears to have enough RAM that most of it
is beyond the device's 36-bit DMA mask, thus it's fairly likely for the
initial direct alloc to come back with something unsuitable.
Robin.
>
>
> thanks,
>
> Takashi
>
>>> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088658
>>> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1088902
>>> Fixes: 0176adb00406 ("swiotlb: refactor coherent buffer allocation")
>>> Cc: <stable@vger.kernel.org> # v4.16+
>>> Signed-off-by: Takashi Iwai <tiwai@suse.de>
>>> ---
>>> lib/swiotlb.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
>>> index 47aeb04c1997..de7cc540450f 100644
>>> --- a/lib/swiotlb.c
>>> +++ b/lib/swiotlb.c
>>> @@ -719,7 +719,7 @@ swiotlb_alloc_buffer(struct device *dev, size_t size, dma_addr_t *dma_handle,
>>> goto out_warn;
>>>
>>> *dma_handle = __phys_to_dma(dev, phys_addr);
>>> - if (dma_coherent_ok(dev, *dma_handle, size))
>>> + if (!dma_coherent_ok(dev, *dma_handle, size))
>>> goto out_unmap;
>>>
>>> memset(phys_to_virt(phys_addr), 0, size);
>>> --
>>> 2.16.3
>> ---end quoted text---
>>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-10 17:50 ` Robin Murphy
@ 2018-04-10 18:10 ` Christoph Hellwig
2018-04-11 7:28 ` Takashi Iwai
0 siblings, 1 reply; 12+ messages in thread
From: Christoph Hellwig @ 2018-04-10 18:10 UTC (permalink / raw)
To: Robin Murphy
Cc: Takashi Iwai, Christoph Hellwig, linux-kernel, iommu,
Christian König, Konrad Rzeszutek Wilk
On Tue, Apr 10, 2018 at 06:50:04PM +0100, Robin Murphy wrote:
> In the first one, the machine appears to have enough RAM that most of it is
> beyond the device's 36-bit DMA mask, thus it's fairly likely for the
> initial direct alloc to come back with something unsuitable.
But we should try a GFP_DMA32 allocation first, so this is a bit
surprising.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-10 18:10 ` Christoph Hellwig
@ 2018-04-11 7:28 ` Takashi Iwai
2018-04-12 6:02 ` Christoph Hellwig
0 siblings, 1 reply; 12+ messages in thread
From: Takashi Iwai @ 2018-04-11 7:28 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Robin Murphy, linux-kernel, iommu, Christian König,
Konrad Rzeszutek Wilk
On Tue, 10 Apr 2018 20:10:20 +0200,
Christoph Hellwig wrote:
>
> On Tue, Apr 10, 2018 at 06:50:04PM +0100, Robin Murphy wrote:
> > In the first one, the machine appears to have enough RAM that most of it is
> > beyond the device's 36-bit DMA mask, thus it's fairly likely for the
> > initial direct alloc to come back with something unsuitable.
>
> But we should try a GFP_DMA32 allocation first, so this is a bit
> surprising.
Hm, do we really try that?
Through a quick glance, dma_alloc_coherent_gfp_flags() gives GFP_DMA32
only when coherent mask <= DMA_BIT_MASK(32); in the case of iwlwifi,
it's 36bit, so GFP_DMA isn't set.
We had a fallback allocation with GFP_DMA32 in the past, but this
seems gone long time ago along with cleanups (commit c647c3bb2d16).
But I haven't followed about this topic for long time, so I might have
missed obviously...
thanks,
Takashi
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-11 7:28 ` Takashi Iwai
@ 2018-04-12 6:02 ` Christoph Hellwig
2018-04-12 8:03 ` Takashi Iwai
0 siblings, 1 reply; 12+ messages in thread
From: Christoph Hellwig @ 2018-04-12 6:02 UTC (permalink / raw)
To: Takashi Iwai
Cc: Christoph Hellwig, Robin Murphy, linux-kernel, iommu,
Christian König, Konrad Rzeszutek Wilk
On Wed, Apr 11, 2018 at 09:28:54AM +0200, Takashi Iwai wrote:
> > But we should try a GFP_DMA32 allocation first, so this is a bit
> > surprising.
>
> Hm, do we really try that?
> Through a quick glance, dma_alloc_coherent_gfp_flags() gives GFP_DMA32
> only when coherent mask <= DMA_BIT_MASK(32); in the case of iwlwifi,
> it's 36bit, so GFP_DMA isn't set.
Oh, yes - it is using an odd dma mask, and amdgpu seems to use an
just as odd 40-bit dma mask.
> We had a fallback allocation with GFP_DMA32 in the past, but this
> seems gone long time ago along with cleanups (commit c647c3bb2d16).
>
> But I haven't followed about this topic for long time, so I might have
> missed obviously...
I think a fallback would be much better here rather than relying on the
limited swiotlb buffer bool. dma_direct_alloc (which in 4.17 is also
used for x86) already has a GFP_DMA fallback, so extending this for
GFP_DMA32 as well would seem reasonable.
Any volunteers?
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-12 6:02 ` Christoph Hellwig
@ 2018-04-12 8:03 ` Takashi Iwai
2018-04-12 8:19 ` Takashi Iwai
0 siblings, 1 reply; 12+ messages in thread
From: Takashi Iwai @ 2018-04-12 8:03 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Takashi Iwai, Robin Murphy, linux-kernel, iommu,
Christian König, Konrad Rzeszutek Wilk
[-- Attachment #1: Type: text/plain, Size: 1370 bytes --]
On Thu, 12 Apr 2018 08:02:27 +0200,
Christoph Hellwig wrote:
>
> On Wed, Apr 11, 2018 at 09:28:54AM +0200, Takashi Iwai wrote:
> > > But we should try a GFP_DMA32 allocation first, so this is a bit
> > > surprising.
> >
> > Hm, do we really try that?
> > Through a quick glance, dma_alloc_coherent_gfp_flags() gives GFP_DMA32
> > only when coherent mask <= DMA_BIT_MASK(32); in the case of iwlwifi,
> > it's 36bit, so GFP_DMA isn't set.
>
> Oh, yes - it is using an odd dma mask, and amdgpu seems to use an
> just as odd 40-bit dma mask.
>
> > We had a fallback allocation with GFP_DMA32 in the past, but this
> > seems gone long time ago along with cleanups (commit c647c3bb2d16).
> >
> > But I haven't followed about this topic for long time, so I might have
> > missed obviously...
>
> I think a fallback would be much better here rather than relying on the
> limited swiotlb buffer bool. dma_direct_alloc (which in 4.17 is also
> used for x86) already has a GFP_DMA fallback, so extending this for
> GFP_DMA32 as well would seem reasonable.
>
> Any volunteers?
Below is a quick attempt, totally untested. Actually the retry with
GFP_DMA is superfluous for archs without it, so the first patch
corrects it. The second patch adds the retry with GFP_DMA32.
I'll resubmit properly if these are OK (and better if anyone could
test them :)
thanks,
Takashi
[-- Attachment #2: 0001-dma-direct-Don-t-repeat-allocation-for-no-op-GFP_DMA.patch --]
[-- Type: application/octet-stream, Size: 1187 bytes --]
>From 490d11cd440d169c8e1a234c1baee3022c2f3464 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 12 Apr 2018 09:46:12 +0200
Subject: [PATCH 1/2] dma-direct: Don't repeat allocation for no-op GFP_DMA
When an allocation with lower dma_coherent mask fails,
dma_direct_alloc() retries the allocation with GFP_DMA. But, it's
useless for architectures that has no GFP_DMA, obviously.
This patch fixes it by adding the check of GFP_DMA before retrying the
allocation.
Fixes: 95f183916d4b ("dma-direct: retry allocations using GFP_DMA for small masks")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
lib/dma-direct.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index c0bba30fef0a..191f96453419 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -84,7 +84,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
__free_pages(page, page_order);
page = NULL;
- if (dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
+ if (GFP_DMA && dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
!(gfp & GFP_DMA)) {
gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
goto again;
--
2.16.3
[-- Attachment #3: 0002-dma-direct-Try-reallocation-with-GFP_DMA32-if-possib.patch --]
[-- Type: application/octet-stream, Size: 1154 bytes --]
>From 48ce0bb0a6b916f5615e24861cd9ba78c98ee33a Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 12 Apr 2018 09:53:48 +0200
Subject: [PATCH 2/2] dma-direct: Try reallocation with GFP_DMA32 if possible
This patch adds a similar fallback reallocation with GFP_DMA32 as
we've done with GFP_DMA. The condition is that the coherent mask is
smaller than 64bit (i.e. some address limitation), and neither GFP_DMA
nor GFP_DMA32 is set beforehand.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
lib/dma-direct.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index 191f96453419..b3cabf06ce90 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -84,6 +84,12 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
__free_pages(page, page_order);
page = NULL;
+ if (GFP_DMA32 && dev->coherent_dma_mask < DMA_BIT_MASK(64) &&
+ !(gfp & (GFP_DMA32 | GFP_DMA))) {
+ gfp |= GFP_DMA32;
+ goto again;
+ }
+
if (GFP_DMA && dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
!(gfp & GFP_DMA)) {
gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
--
2.16.3
^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-12 8:03 ` Takashi Iwai
@ 2018-04-12 8:19 ` Takashi Iwai
2018-04-12 8:27 ` Takashi Iwai
0 siblings, 1 reply; 12+ messages in thread
From: Takashi Iwai @ 2018-04-12 8:19 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Robin Murphy, linux-kernel, iommu, Christian König,
Konrad Rzeszutek Wilk
On Thu, 12 Apr 2018 10:03:56 +0200,
Takashi Iwai wrote:
>
> On Thu, 12 Apr 2018 08:02:27 +0200,
> Christoph Hellwig wrote:
> >
> > On Wed, Apr 11, 2018 at 09:28:54AM +0200, Takashi Iwai wrote:
> > > > But we should try a GFP_DMA32 allocation first, so this is a bit
> > > > surprising.
> > >
> > > Hm, do we really try that?
> > > Through a quick glance, dma_alloc_coherent_gfp_flags() gives GFP_DMA32
> > > only when coherent mask <= DMA_BIT_MASK(32); in the case of iwlwifi,
> > > it's 36bit, so GFP_DMA isn't set.
> >
> > Oh, yes - it is using an odd dma mask, and amdgpu seems to use an
> > just as odd 40-bit dma mask.
> >
> > > We had a fallback allocation with GFP_DMA32 in the past, but this
> > > seems gone long time ago along with cleanups (commit c647c3bb2d16).
> > >
> > > But I haven't followed about this topic for long time, so I might have
> > > missed obviously...
> >
> > I think a fallback would be much better here rather than relying on the
> > limited swiotlb buffer bool. dma_direct_alloc (which in 4.17 is also
> > used for x86) already has a GFP_DMA fallback, so extending this for
> > GFP_DMA32 as well would seem reasonable.
> >
> > Any volunteers?
>
> Below is a quick attempt, totally untested. Actually the retry with
> GFP_DMA is superfluous for archs without it, so the first patch
> corrects it.
Gah, scratch this, it doesn't work. A different check is needed...
Takashi
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-12 8:19 ` Takashi Iwai
@ 2018-04-12 8:27 ` Takashi Iwai
2018-04-12 10:32 ` Robin Murphy
0 siblings, 1 reply; 12+ messages in thread
From: Takashi Iwai @ 2018-04-12 8:27 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Robin Murphy, linux-kernel, iommu, Christian König,
Konrad Rzeszutek Wilk
[-- Attachment #1: Type: text/plain, Size: 1622 bytes --]
On Thu, 12 Apr 2018 10:19:05 +0200,
Takashi Iwai wrote:
>
> On Thu, 12 Apr 2018 10:03:56 +0200,
> Takashi Iwai wrote:
> >
> > On Thu, 12 Apr 2018 08:02:27 +0200,
> > Christoph Hellwig wrote:
> > >
> > > On Wed, Apr 11, 2018 at 09:28:54AM +0200, Takashi Iwai wrote:
> > > > > But we should try a GFP_DMA32 allocation first, so this is a bit
> > > > > surprising.
> > > >
> > > > Hm, do we really try that?
> > > > Through a quick glance, dma_alloc_coherent_gfp_flags() gives GFP_DMA32
> > > > only when coherent mask <= DMA_BIT_MASK(32); in the case of iwlwifi,
> > > > it's 36bit, so GFP_DMA isn't set.
> > >
> > > Oh, yes - it is using an odd dma mask, and amdgpu seems to use an
> > > just as odd 40-bit dma mask.
> > >
> > > > We had a fallback allocation with GFP_DMA32 in the past, but this
> > > > seems gone long time ago along with cleanups (commit c647c3bb2d16).
> > > >
> > > > But I haven't followed about this topic for long time, so I might have
> > > > missed obviously...
> > >
> > > I think a fallback would be much better here rather than relying on the
> > > limited swiotlb buffer bool. dma_direct_alloc (which in 4.17 is also
> > > used for x86) already has a GFP_DMA fallback, so extending this for
> > > GFP_DMA32 as well would seem reasonable.
> > >
> > > Any volunteers?
> >
> > Below is a quick attempt, totally untested. Actually the retry with
> > GFP_DMA is superfluous for archs without it, so the first patch
> > corrects it.
>
> Gah, scratch this, it doesn't work. A different check is needed...
The v2 patches are below, replaced with IS_ENABLED(CONFIG_ZONE_DMA).
Takashi
[-- Attachment #2: 0001-dma-direct-Don-t-repeat-allocation-for-no-op-GFP_DMA.patch --]
[-- Type: application/octet-stream, Size: 1228 bytes --]
>From 8d320bed20265ea98087a2b9c4abf2b4bf9cb9ec Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 12 Apr 2018 09:46:12 +0200
Subject: [PATCH v2 1/2] dma-direct: Don't repeat allocation for no-op GFP_DMA
When an allocation with lower dma_coherent mask fails,
dma_direct_alloc() retries the allocation with GFP_DMA. But, it's
useless for architectures that has no ZONE_DMA, obviously.
This patch fixes it by adding the check of CONFIG_ZONE_DMA before
retrying the allocation.
Fixes: 95f183916d4b ("dma-direct: retry allocations using GFP_DMA for small masks")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
lib/dma-direct.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index c0bba30fef0a..bbfb229aa067 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -84,7 +84,8 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
__free_pages(page, page_order);
page = NULL;
- if (dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
+ if (IS_ENABLED(CONFIG_ZONE_DMA) &&
+ dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
!(gfp & GFP_DMA)) {
gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
goto again;
--
2.16.3
[-- Attachment #3: 0002-dma-direct-Try-reallocation-with-GFP_DMA32-if-possib.patch --]
[-- Type: application/octet-stream, Size: 1173 bytes --]
>From 0d3781b8c0c397768c29c0351390f0fa04c9eaa8 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 12 Apr 2018 09:53:48 +0200
Subject: [PATCH v2 2/2] dma-direct: Try reallocation with GFP_DMA32 if
possible
This patch adds a similar fallback reallocation with GFP_DMA32 as
we've done with GFP_DMA. The condition is that the coherent mask is
smaller than 64bit (i.e. some address limitation), and neither GFP_DMA
nor GFP_DMA32 is set beforehand.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
lib/dma-direct.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index bbfb229aa067..970d39155618 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -84,6 +84,13 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
__free_pages(page, page_order);
page = NULL;
+ if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
+ dev->coherent_dma_mask < DMA_BIT_MASK(64) &&
+ !(gfp & (GFP_DMA32 | GFP_DMA))) {
+ gfp |= GFP_DMA32;
+ goto again;
+ }
+
if (IS_ENABLED(CONFIG_ZONE_DMA) &&
dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
!(gfp & GFP_DMA)) {
--
2.16.3
^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-12 8:27 ` Takashi Iwai
@ 2018-04-12 10:32 ` Robin Murphy
2018-04-15 8:43 ` Takashi Iwai
0 siblings, 1 reply; 12+ messages in thread
From: Robin Murphy @ 2018-04-12 10:32 UTC (permalink / raw)
To: Takashi Iwai, Christoph Hellwig
Cc: iommu, Konrad Rzeszutek Wilk, linux-kernel, Christian König
On 12/04/18 09:27, Takashi Iwai wrote:
> On Thu, 12 Apr 2018 10:19:05 +0200,
> Takashi Iwai wrote:
>>
>> On Thu, 12 Apr 2018 10:03:56 +0200,
>> Takashi Iwai wrote:
>>>
>>> On Thu, 12 Apr 2018 08:02:27 +0200,
>>> Christoph Hellwig wrote:
>>>>
>>>> On Wed, Apr 11, 2018 at 09:28:54AM +0200, Takashi Iwai wrote:
>>>>>> But we should try a GFP_DMA32 allocation first, so this is a bit
>>>>>> surprising.
>>>>>
>>>>> Hm, do we really try that?
>>>>> Through a quick glance, dma_alloc_coherent_gfp_flags() gives GFP_DMA32
>>>>> only when coherent mask <= DMA_BIT_MASK(32); in the case of iwlwifi,
>>>>> it's 36bit, so GFP_DMA isn't set.
>>>>
>>>> Oh, yes - it is using an odd dma mask, and amdgpu seems to use an
>>>> just as odd 40-bit dma mask.
>>>>
>>>>> We had a fallback allocation with GFP_DMA32 in the past, but this
>>>>> seems gone long time ago along with cleanups (commit c647c3bb2d16).
>>>>>
>>>>> But I haven't followed about this topic for long time, so I might have
>>>>> missed obviously...
>>>>
>>>> I think a fallback would be much better here rather than relying on the
>>>> limited swiotlb buffer bool. dma_direct_alloc (which in 4.17 is also
>>>> used for x86) already has a GFP_DMA fallback, so extending this for
>>>> GFP_DMA32 as well would seem reasonable.
>>>>
>>>> Any volunteers?
>>>
>>> Below is a quick attempt, totally untested. Actually the retry with
>>> GFP_DMA is superfluous for archs without it, so the first patch
>>> corrects it.
>>
>> Gah, scratch this, it doesn't work. A different check is needed...
>
> The v2 patches are below, replaced with IS_ENABLED(CONFIG_ZONE_DMA).
That looks pretty reasonable to me - I'd be tempted to try a factoring
out a helper function to avoid the "goto again" logic, but that's hardly
crucial.
What I'd really love to see is something like the alloc_pages_mask()
proposal from years ago to come back such that GFP_DMA32 could die
entirely, but I don't know anywhere near enough about the mm layer to
consider taking that on myself :(
Robin.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures
2018-04-12 10:32 ` Robin Murphy
@ 2018-04-15 8:43 ` Takashi Iwai
0 siblings, 0 replies; 12+ messages in thread
From: Takashi Iwai @ 2018-04-15 8:43 UTC (permalink / raw)
To: Robin Murphy
Cc: Takashi Iwai, Christoph Hellwig, iommu, Konrad Rzeszutek Wilk,
linux-kernel, Christian K6nig
On Thu, 12 Apr 2018 12:32:54 +0200,
Robin Murphy wrote:
>
> On 12/04/18 09:27, Takashi Iwai wrote:
> > On Thu, 12 Apr 2018 10:19:05 +0200,
> > Takashi Iwai wrote:
> >>
> >> On Thu, 12 Apr 2018 10:03:56 +0200,
> >> Takashi Iwai wrote:
> >>>
> >>> On Thu, 12 Apr 2018 08:02:27 +0200,
> >>> Christoph Hellwig wrote:
> >>>>
> >>>> On Wed, Apr 11, 2018 at 09:28:54AM +0200, Takashi Iwai wrote:
> >>>>>> But we should try a GFP_DMA32 allocation first, so this is a bit
> >>>>>> surprising.
> >>>>>
> >>>>> Hm, do we really try that?
> >>>>> Through a quick glance, dma_alloc_coherent_gfp_flags() gives GFP_DMA32
> >>>>> only when coherent mask <= DMA_BIT_MASK(32); in the case of iwlwifi,
> >>>>> it's 36bit, so GFP_DMA isn't set.
> >>>>
> >>>> Oh, yes - it is using an odd dma mask, and amdgpu seems to use an
> >>>> just as odd 40-bit dma mask.
> >>>>
> >>>>> We had a fallback allocation with GFP_DMA32 in the past, but this
> >>>>> seems gone long time ago along with cleanups (commit c647c3bb2d16).
> >>>>>
> >>>>> But I haven't followed about this topic for long time, so I might have
> >>>>> missed obviously...
> >>>>
> >>>> I think a fallback would be much better here rather than relying on the
> >>>> limited swiotlb buffer bool. dma_direct_alloc (which in 4.17 is also
> >>>> used for x86) already has a GFP_DMA fallback, so extending this for
> >>>> GFP_DMA32 as well would seem reasonable.
> >>>>
> >>>> Any volunteers?
> >>>
> >>> Below is a quick attempt, totally untested. Actually the retry with
> >>> GFP_DMA is superfluous for archs without it, so the first patch
> >>> corrects it.
> >>
> >> Gah, scratch this, it doesn't work. A different check is needed...
> >
> > The v2 patches are below, replaced with IS_ENABLED(CONFIG_ZONE_DMA).
>
> That looks pretty reasonable to me - I'd be tempted to try a factoring
> out a helper function to avoid the "goto again" logic, but that's
> hardly crucial.
Right, this change won't make the code flow more complex than before,
so I guess it's OK as a first step.
I'll submit this second patch as RFC while the first one as a safe
fix (in addition to another regression fix I stumbled on).
> What I'd really love to see is something like the alloc_pages_mask()
> proposal from years ago to come back such that GFP_DMA32 could die
> entirely, but I don't know anywhere near enough about the mm layer to
> consider taking that on myself :(
Yeah, it'd be lovely, but I'm afraid it's hard to fly high...
thanks,
Takashi
^ permalink raw reply [flat|nested] 12+ messages in thread
end of thread, other threads:[~2018-04-15 8:43 UTC | newest]
Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-04-10 17:05 [PATCH] swiotlb: Fix unexpected swiotlb_alloc_coherent() failures Takashi Iwai
2018-04-10 17:06 ` Christoph Hellwig
2018-04-10 17:07 ` Takashi Iwai
2018-04-10 17:50 ` Robin Murphy
2018-04-10 18:10 ` Christoph Hellwig
2018-04-11 7:28 ` Takashi Iwai
2018-04-12 6:02 ` Christoph Hellwig
2018-04-12 8:03 ` Takashi Iwai
2018-04-12 8:19 ` Takashi Iwai
2018-04-12 8:27 ` Takashi Iwai
2018-04-12 10:32 ` Robin Murphy
2018-04-15 8:43 ` Takashi Iwai
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