Re: 答复: [PATCH] drm/amdgpu: adjust gtt memory size

[Christian König]

Am 21.07.2016 um 11:16 schrieb Wang, Qingqing:
>
> This doesn't work on 32bit systems since totalram is a long (IIRC) and
> so this will certainly overflow.
>
> -- can you be more specific, how could the overflow happen?
>

Both values are 32bit on a 32bit system, so as soon as you have more 
than 4GB installed this will overflow.

You need to cast the long to a 64bit value to avoid that.

>
> Additional if I remember correctly we didn't ended the discussion on
> what to do here with a conclusion.
>
> -- ok, since it happens in anther mail list, we should stop talking 
> about it here, you can send out your ideas there.
>

Actually that discussion was held long ago internally but we never got a 
conclusion on this IIRC. So we should probably continue the discussion 
on this thread now.

Regards,
Christian.

> ------------------------------------------------------------------------
> *发件人:* amd-gfx <amd-gfx-bounces at lists.freedesktop.org> 代表 Christian 
> König <deathsimple at vodafone.de>
> *发送时间:* 2016年7月21日 16:53:05
> *收件人:* Wang, Qingqing; amd-gfx at lists.freedesktop.org
> *主题:* Re: [PATCH] drm/amdgpu: adjust gtt memory size
> Am 21.07.2016 um 09:46 schrieb Ken Wang:
> > Change-Id: If00d5b97ba9e30f9b7f68fdfc134a0f8b3ad2add
> > Signed-off-by: Ken Wang <Qingqing.Wang at amd.com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c | 7 ++++++-
> >   drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c | 7 ++++++-
> >   2 files changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c 
> b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> > index a3b6048..0b095d5 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v7_0.c
> > @@ -336,6 +336,11 @@ static int gmc_v7_0_mc_init(struct 
> amdgpu_device *adev)
> >   {
> >        u32 tmp;
> >        int chansize, numchan;
> > +     u64 sysmem_size;
> > +     struct sysinfo si;
> > +
> > +     si_meminfo(&si);
> > +     sysmem_size = si.totalram * si.mem_unit;
>
> This doesn't work on 32bit systems since totalram is a long (IIRC) and
> so this will certainly overflow.
>
> Additional if I remember correctly we didn't ended the discussion on
> what to do here with a conclusion.
>
> Regards,
> Christian.
>
> >
> >        /* Get VRAM informations */
> >        tmp = RREG32(mmMC_ARB_RAMCFG);
> > @@ -392,7 +397,7 @@ static int gmc_v7_0_mc_init(struct amdgpu_device 
> *adev)
> >         * size equal to the 1024 or vram, whichever is larger.
> >         */
> >        if (amdgpu_gart_size == -1)
> > -             adev->mc.gtt_size = max((1024ULL << 20), 
> adev->mc.mc_vram_size);
> > +             adev->mc.gtt_size = max((1024ULL << 20), 
> min(adev->mc.mc_vram_size, sysmem_size/2));
> >        else
> >                adev->mc.gtt_size = (uint64_t)amdgpu_gart_size << 20;
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c 
> b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
> > index 02b6872..790bf7a 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v8_0.c
> > @@ -413,6 +413,11 @@ static int gmc_v8_0_mc_init(struct 
> amdgpu_device *adev)
> >   {
> >        u32 tmp;
> >        int chansize, numchan;
> > +     u64 sysmem_size;
> > +     struct sysinfo si;
> > +
> > +     si_meminfo(&si);
> > +     sysmem_size = si.totalram * si.mem_unit;
> >
> >        /* Get VRAM informations */
> >        tmp = RREG32(mmMC_ARB_RAMCFG);
> > @@ -469,7 +474,7 @@ static int gmc_v8_0_mc_init(struct amdgpu_device 
> *adev)
> >         * size equal to the 1024 or vram, whichever is larger.
> >         */
> >        if (amdgpu_gart_size == -1)
> > -             adev->mc.gtt_size = max((1024ULL << 20), 
> adev->mc.mc_vram_size);
> > +             adev->mc.gtt_size = max((1024ULL << 20), 
> min(adev->mc.mc_vram_size, sysmem_size/2));
> >        else
> >                adev->mc.gtt_size = (uint64_t)amdgpu_gart_size << 20;
> >
>
>
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