Re: [PATCH v3 1/1] drm/ttm: Fix COW check

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jul 23, 2021 at 10:33:48AM +0200, Christian König wrote:
> 
> 
> Am 23.07.21 um 10:21 schrieb Daniel Vetter:
> > On Wed, Jul 14, 2021 at 10:51 AM Christian König
> > <christian.koenig@amd.com> wrote:
> > > 
> > > 
> > > Am 13.07.21 um 17:28 schrieb Alex Deucher:
> > > > On Tue, Jul 13, 2021 at 2:57 AM Christian König
> > > > <ckoenig.leichtzumerken@gmail.com> wrote:
> > > > > 
> > > > > Am 13.07.21 um 00:06 schrieb Felix Kuehling:
> > > > > > KFD Thunk maps invisible VRAM BOs with PROT_NONE, MAP_PRIVATE.
> > > > > > is_cow_mapping returns true for these mappings. Add a check for
> > > > > > vm_flags & VM_WRITE to avoid mmap failures on private read-only or
> > > > > > PROT_NONE mappings.
> > > > > > 
> > > > > > v2: protect against mprotect making a mapping writable after the fact
> > > > > > v3: update driver-specific vm_operations_structs
> > > > > > 
> > > > > > Fixes: f91142c62161 ("drm/ttm: nuke VM_MIXEDMAP on BO mappings v3")
> > > > > > Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
> > > > > > Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
> > > > > Reviewed-by: Christian König <christian.koenig@amd.com>
> > > > Are you planning to push this to drm-misc?
> > > Yes, just didn't found time yesterday.
> > This is pushed to the wrong tree drm-misc-next-fixes, should have been
> > in drm-misc-fixes. Please be careful with that because every time that
> > goes wrong the script gets confused about which the current tree is,
> > and pushes the wrong tree to linux-next branches.
> > 
> > I'm going to hard-reset drm-misc-next-fixes now and hope that's good
> > enough to fix things up (since Thomas is not around all the time for
> > this merge window).
> 
> STOP! I'm about to push a revert for this patch.
> 
> And yes that was pushed to the wrong branch, but it turned out that this was
> fortunate since the patch doesn't work correctly.

Well I just hard-reset, so you can push the right patch to the right
branch now. The trouble is that outside of the merge window no one is
allowed to push to drm-misc-next-fixes. If you do, then dim pushes
drm-misc-next-fixes to for-linux-next instead of drm-misc-next, and we
have bad surprises.

Which unfortunately happens like every merge window a few times and always
takes a few days/weeks to get caught.
-Danie

> 
> Christian.
> 
> > -Daniel
> > 
> > 
> > > Christian.
> > > 
> > > > Alex
> > > > 
> > > > > > ---
> > > > > >     drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c  |  3 ++-
> > > > > >     drivers/gpu/drm/nouveau/nouveau_gem.c    |  3 ++-
> > > > > >     drivers/gpu/drm/radeon/radeon_gem.c      |  3 ++-
> > > > > >     drivers/gpu/drm/ttm/ttm_bo_vm.c          | 14 +++++++++++++-
> > > > > >     drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c |  1 +
> > > > > >     include/drm/ttm/ttm_bo_api.h             |  4 ++++
> > > > > >     6 files changed, 24 insertions(+), 4 deletions(-)
> > > > > > 
> > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> > > > > > index b3404c43a911..1aa750a6a5d2 100644
> > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> > > > > > @@ -79,7 +79,8 @@ static const struct vm_operations_struct amdgpu_gem_vm_ops = {
> > > > > >         .fault = amdgpu_gem_fault,
> > > > > >         .open = ttm_bo_vm_open,
> > > > > >         .close = ttm_bo_vm_close,
> > > > > > -     .access = ttm_bo_vm_access
> > > > > > +     .access = ttm_bo_vm_access,
> > > > > > +     .mprotect = ttm_bo_vm_mprotect
> > > > > >     };
> > > > > > 
> > > > > >     static void amdgpu_gem_object_free(struct drm_gem_object *gobj)
> > > > > > diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
> > > > > > index 5b27845075a1..164ea564bb7a 100644
> > > > > > --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> > > > > > +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> > > > > > @@ -70,7 +70,8 @@ static const struct vm_operations_struct nouveau_ttm_vm_ops = {
> > > > > >         .fault = nouveau_ttm_fault,
> > > > > >         .open = ttm_bo_vm_open,
> > > > > >         .close = ttm_bo_vm_close,
> > > > > > -     .access = ttm_bo_vm_access
> > > > > > +     .access = ttm_bo_vm_access,
> > > > > > +     .mprotect = ttm_bo_vm_mprotect
> > > > > >     };
> > > > > > 
> > > > > >     void
> > > > > > diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
> > > > > > index 458f92a70887..c19ad07eb7b5 100644
> > > > > > --- a/drivers/gpu/drm/radeon/radeon_gem.c
> > > > > > +++ b/drivers/gpu/drm/radeon/radeon_gem.c
> > > > > > @@ -77,7 +77,8 @@ static const struct vm_operations_struct radeon_gem_vm_ops = {
> > > > > >         .fault = radeon_gem_fault,
> > > > > >         .open = ttm_bo_vm_open,
> > > > > >         .close = ttm_bo_vm_close,
> > > > > > -     .access = ttm_bo_vm_access
> > > > > > +     .access = ttm_bo_vm_access,
> > > > > > +     .mprotect = ttm_bo_vm_mprotect
> > > > > >     };
> > > > > > 
> > > > > >     static void radeon_gem_object_free(struct drm_gem_object *gobj)
> > > > > > diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > > > > index f56be5bc0861..fb325bad5db6 100644
> > > > > > --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > > > > +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > > > > @@ -542,17 +542,29 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> > > > > >     }
> > > > > >     EXPORT_SYMBOL(ttm_bo_vm_access);
> > > > > > 
> > > > > > +int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
> > > > > > +                    unsigned long end, unsigned long newflags)
> > > > > > +{
> > > > > > +     /* Enforce no COW since would have really strange behavior with it. */
> > > > > > +     if (is_cow_mapping(newflags) && (newflags & VM_WRITE))
> > > > > > +             return -EINVAL;
> > > > > > +
> > > > > > +     return 0;
> > > > > > +}
> > > > > > +EXPORT_SYMBOL(ttm_bo_vm_mprotect);
> > > > > > +
> > > > > >     static const struct vm_operations_struct ttm_bo_vm_ops = {
> > > > > >         .fault = ttm_bo_vm_fault,
> > > > > >         .open = ttm_bo_vm_open,
> > > > > >         .close = ttm_bo_vm_close,
> > > > > >         .access = ttm_bo_vm_access,
> > > > > > +     .mprotect = ttm_bo_vm_mprotect,
> > > > > >     };
> > > > > > 
> > > > > >     int ttm_bo_mmap_obj(struct vm_area_struct *vma, struct ttm_buffer_object *bo)
> > > > > >     {
> > > > > >         /* Enforce no COW since would have really strange behavior with it. */
> > > > > > -     if (is_cow_mapping(vma->vm_flags))
> > > > > > +     if (is_cow_mapping(vma->vm_flags) && (vma->vm_flags & VM_WRITE))
> > > > > >                 return -EINVAL;
> > > > > > 
> > > > > >         ttm_bo_get(bo);
> > > > > > diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
> > > > > > index e6b1f98ec99f..e4bf7dc99320 100644
> > > > > > --- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
> > > > > > +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
> > > > > > @@ -61,6 +61,7 @@ int vmw_mmap(struct file *filp, struct vm_area_struct *vma)
> > > > > >                 .fault = vmw_bo_vm_fault,
> > > > > >                 .open = ttm_bo_vm_open,
> > > > > >                 .close = ttm_bo_vm_close,
> > > > > > +             .mprotect = ttm_bo_vm_mprotect,
> > > > > >     #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> > > > > >                 .huge_fault = vmw_bo_vm_huge_fault,
> > > > > >     #endif
> > > > > > diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
> > > > > > index f681bbdbc698..40eb95875355 100644
> > > > > > --- a/include/drm/ttm/ttm_bo_api.h
> > > > > > +++ b/include/drm/ttm/ttm_bo_api.h
> > > > > > @@ -605,6 +605,10 @@ void ttm_bo_vm_close(struct vm_area_struct *vma);
> > > > > > 
> > > > > >     int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> > > > > >                      void *buf, int len, int write);
> > > > > > +
> > > > > > +int ttm_bo_vm_mprotect(struct vm_area_struct *vma, unsigned long start,
> > > > > > +                    unsigned long end, unsigned long newflags);
> > > > > > +
> > > > > >     bool ttm_bo_delayed_delete(struct ttm_device *bdev, bool remove_all);
> > > > > > 
> > > > > >     vm_fault_t ttm_bo_vm_dummy_page(struct vm_fault *vmf, pgprot_t prot);
> > 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch