Re: [PATCH] drm/amdgpu: potential shift wrapping bug
Am 10.08.2017 15:02, schrieb Christian König:
> Am 10.08.2017 um 14:53 schrieb Dan Carpenter:
>> On Thu, Aug 10, 2017 at 02:30:15PM +0200, Christian König wrote:
>>> Am 10.08.2017 um 14:16 schrieb Dan Carpenter:
"frag_align" is a u64, so presumably we want to use the high bits as
well instead of shift wrapping.
Fixes: 6be7adb37d9b ("drm/amdgpu: increase fragmentation size for
Vega10 v2")
Signed-off-by: Dan Carpenter
>>> The fragment field has only 5bits in hardware and can never be more
>>> than 31,
>>> so the correct fix would actually be using uint32_t here instead.
>>>
>> Changing it to uint32_t introduces a new static checker warning:
>>
>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:1465 amdgpu_vm_frag_ptes()
>> warn: was expecting a 64 bit value instead of '~(frag_align - 1)'
>>
>> Unfortunately, I get so many thousands of those I can't normally even
>> review that sort of bug...
>>
>> Let me resend the original patch but with a modified changelog to say
>> that the bug is a false positive.
>
> Ah, yes of course that's why I made it a 64bit value in the first place.
>
> Mhm, could we use something like (u32)(1 << pages_per_frag) instead to
> silence the static checker warning?
>
> It doesn't make much sense to use a 64bit shift here.
>
> Christian.
>
Why not keeping Dan 1. patch and add a comment that pages_per_frag is always
>31 ?
Using 32bit in a 64bit is not forbidden, and changing it causes more problems
than
it solves. But doing so should be done in a clean way.
just my 2 cents,
re,
wh
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Re: [PATCH] drm/amdgpu: potential shift wrapping bug
Am 10.08.2017 um 14:53 schrieb Dan Carpenter:
On Thu, Aug 10, 2017 at 02:30:15PM +0200, Christian König wrote:
Am 10.08.2017 um 14:16 schrieb Dan Carpenter:
"frag_align" is a u64, so presumably we want to use the high bits as
well instead of shift wrapping.
Fixes: 6be7adb37d9b ("drm/amdgpu: increase fragmentation size for Vega10 v2")
Signed-off-by: Dan Carpenter
The fragment field has only 5bits in hardware and can never be more than 31,
so the correct fix would actually be using uint32_t here instead.
Changing it to uint32_t introduces a new static checker warning:
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:1465 amdgpu_vm_frag_ptes()
warn: was expecting a 64 bit value instead of '~(frag_align - 1)'
Unfortunately, I get so many thousands of those I can't normally even
review that sort of bug...
Let me resend the original patch but with a modified changelog to say
that the bug is a false positive.
Ah, yes of course that's why I made it a 64bit value in the first place.
Mhm, could we use something like (u32)(1 << pages_per_frag) instead to
silence the static checker warning?
It doesn't make much sense to use a 64bit shift here.
Christian.
regards,
dan carpenter
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Re: [PATCH] drm/amdgpu: potential shift wrapping bug
On Thu, Aug 10, 2017 at 03:02:53PM +0200, Christian König wrote:
> Am 10.08.2017 um 14:53 schrieb Dan Carpenter:
> > On Thu, Aug 10, 2017 at 02:30:15PM +0200, Christian König wrote:
> > > Am 10.08.2017 um 14:16 schrieb Dan Carpenter:
> > > > "frag_align" is a u64, so presumably we want to use the high bits as
> > > > well instead of shift wrapping.
> > > >
> > > > Fixes: 6be7adb37d9b ("drm/amdgpu: increase fragmentation size for
> > > > Vega10 v2")
> > > > Signed-off-by: Dan Carpenter
> > > The fragment field has only 5bits in hardware and can never be more than
> > > 31,
> > > so the correct fix would actually be using uint32_t here instead.
> > >
> > Changing it to uint32_t introduces a new static checker warning:
> >
> > drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:1465 amdgpu_vm_frag_ptes()
> > warn: was expecting a 64 bit value instead of '~(frag_align - 1)'
> >
> > Unfortunately, I get so many thousands of those I can't normally even
> > review that sort of bug...
> >
> > Let me resend the original patch but with a modified changelog to say
> > that the bug is a false positive.
>
> Ah, yes of course that's why I made it a 64bit value in the first place.
>
> Mhm, could we use something like (u32)(1 << pages_per_frag) instead to
> silence the static checker warning?
That wouldn't silence it and I think that's not super pretty either.
>
> It doesn't make much sense to use a 64bit shift here.
>
I'm just going to ignore the warning. This driver isn't part of my
.config so I'm not really compiling it the way it was designed which
means I don't have the cross function database enabled. Probably if I
compiled this normally, I wouldn't even get the warning.
regards,
dan carpenter
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Re: [PATCH] drm/amdgpu: potential shift wrapping bug
On Thu, Aug 10, 2017 at 02:30:15PM +0200, Christian König wrote:
> Am 10.08.2017 um 14:16 schrieb Dan Carpenter:
> > "frag_align" is a u64, so presumably we want to use the high bits as
> > well instead of shift wrapping.
> >
> > Fixes: 6be7adb37d9b ("drm/amdgpu: increase fragmentation size for Vega10
> > v2")
> > Signed-off-by: Dan Carpenter
>
> The fragment field has only 5bits in hardware and can never be more than 31,
> so the correct fix would actually be using uint32_t here instead.
>
Changing it to uint32_t introduces a new static checker warning:
drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c:1465 amdgpu_vm_frag_ptes()
warn: was expecting a 64 bit value instead of '~(frag_align - 1)'
Unfortunately, I get so many thousands of those I can't normally even
review that sort of bug...
Let me resend the original patch but with a modified changelog to say
that the bug is a false positive.
regards,
dan carpenter
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Re: [PATCH] drm/amdgpu: potential shift wrapping bug
On Thu, Aug 10, 2017 at 02:30:15PM +0200, Christian König wrote:
> Am 10.08.2017 um 14:16 schrieb Dan Carpenter:
> > "frag_align" is a u64, so presumably we want to use the high bits as
> > well instead of shift wrapping.
> >
> > Fixes: 6be7adb37d9b ("drm/amdgpu: increase fragmentation size for Vega10
> > v2")
> > Signed-off-by: Dan Carpenter
>
> The fragment field has only 5bits in hardware and can never be more than 31,
> so the correct fix would actually be using uint32_t here instead.
>
Alright. Thanks. I'll resend.
regards,
dan carpenter
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Re: [PATCH] drm/amdgpu: potential shift wrapping bug
Am 10.08.2017 um 14:16 schrieb Dan Carpenter:
"frag_align" is a u64, so presumably we want to use the high bits as
well instead of shift wrapping.
Fixes: 6be7adb37d9b ("drm/amdgpu: increase fragmentation size for Vega10 v2")
Signed-off-by: Dan Carpenter
The fragment field has only 5bits in hardware and can never be more than
31, so the correct fix would actually be using uint32_t here instead.
Christian.
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index ba0407d12525..d9a8e942ac3b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1459,7 +1459,7 @@ static int amdgpu_vm_frag_ptes(struct
amdgpu_pte_update_params*params,
/* SI and newer are optimized for 64KB */
unsigned pages_per_frag = AMDGPU_LOG2_PAGES_PER_FRAG(params->adev);
uint64_t frag_flags = AMDGPU_PTE_FRAG(pages_per_frag);
- uint64_t frag_align = 1 << pages_per_frag;
+ uint64_t frag_align = 1ULL << pages_per_frag;
uint64_t frag_start = ALIGN(start, frag_align);
uint64_t frag_end = end & ~(frag_align - 1);
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[PATCH] drm/amdgpu: potential shift wrapping bug
"frag_align" is a u64, so presumably we want to use the high bits as
well instead of shift wrapping.
Fixes: 6be7adb37d9b ("drm/amdgpu: increase fragmentation size for Vega10 v2")
Signed-off-by: Dan Carpenter
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index ba0407d12525..d9a8e942ac3b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1459,7 +1459,7 @@ static int amdgpu_vm_frag_ptes(struct
amdgpu_pte_update_params*params,
/* SI and newer are optimized for 64KB */
unsigned pages_per_frag = AMDGPU_LOG2_PAGES_PER_FRAG(params->adev);
uint64_t frag_flags = AMDGPU_PTE_FRAG(pages_per_frag);
- uint64_t frag_align = 1 << pages_per_frag;
+ uint64_t frag_align = 1ULL << pages_per_frag;
uint64_t frag_start = ALIGN(start, frag_align);
uint64_t frag_end = end & ~(frag_align - 1);
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