[RFC PATCH 1/1] drm/ttm, drm/xe: Add ttm_bo_access
Matthew Brost
matthew.brost at intel.com
Fri Oct 18 16:25:33 UTC 2024
On Fri, Oct 18, 2024 at 10:08:06AM +0100, Matthew Auld wrote:
> On 18/10/2024 00:39, Matthew Brost wrote:
> > Non-contiguous VRAM cannot be mapped in Xe nor can non-visible VRAM
> > easily be accessed. Add ttm_bo_access, which is similar to
> > ttm_bo_vm_access, to access such memory.
>
> Is the plan to roll this out also to object error capture and clear color
> access? Those places seem to be using ttm vmap/kmap which only seems to work
> with contiguous VRAM, but in those cases we are mapping userspace objects
> which are potentially not contiguous so I assume that stuff is also quite
> broken atm?
>
I quickly sent this out without checking the error capture code, but
that seems to be broken but no one is complaining? Seems odd.
Let me look into this a bit more before posting a proper series. Will
also update the error capture if needed.
> >
> > Visible VRAM access is only supported at the momement but a follow up
> > can add GPU access to non-visible VRAM.
> >
> > Suggested-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > ---
> > drivers/gpu/drm/ttm/ttm_bo_vm.c | 20 +++++++++-----
> > drivers/gpu/drm/xe/xe_bo.c | 48 +++++++++++++++++++++++++++++++++
> > include/drm/ttm/ttm_bo.h | 2 ++
> > 3 files changed, 64 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > index 2c699ed1963a..b53cc064da44 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > @@ -405,13 +405,9 @@ static int ttm_bo_vm_access_kmap(struct ttm_buffer_object *bo,
> > return len;
> > }
> > -int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> > - void *buf, int len, int write)
> > +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
> > + void *buf, int len, int write)
> > {
> > - struct ttm_buffer_object *bo = vma->vm_private_data;
> > - unsigned long offset = (addr) - vma->vm_start +
> > - ((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
> > - << PAGE_SHIFT);
> > int ret;
> > if (len < 1 || (offset + len) > bo->base.size)
> > @@ -439,6 +435,18 @@ int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> > return ret;
> > }
> > +EXPORT_SYMBOL(ttm_bo_access);
> > +
> > +int ttm_bo_vm_access(struct vm_area_struct *vma, unsigned long addr,
> > + void *buf, int len, int write)
> > +{
> > + struct ttm_buffer_object *bo = vma->vm_private_data;
> > + unsigned long offset = (addr) - vma->vm_start +
> > + ((vma->vm_pgoff - drm_vma_node_start(&bo->base.vma_node))
> > + << PAGE_SHIFT);
> > +
> > + return ttm_bo_access(bo, offset, buf, len, write);
> > +}
> > EXPORT_SYMBOL(ttm_bo_vm_access);
> > static const struct vm_operations_struct ttm_bo_vm_ops = {
> > diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> > index 5b232f2951b1..267f3b03a6d0 100644
> > --- a/drivers/gpu/drm/xe/xe_bo.c
> > +++ b/drivers/gpu/drm/xe/xe_bo.c
> > @@ -1111,6 +1111,53 @@ static void xe_ttm_bo_swap_notify(struct ttm_buffer_object *ttm_bo)
> > }
> > }
> > +static int xe_ttm_access_memory(struct ttm_buffer_object *ttm_bo,
> > + unsigned long offset, void *buf, int len,
> > + int write)
> > +{
> > + struct xe_bo *bo = ttm_to_xe_bo(ttm_bo);
> > + struct xe_device *xe = ttm_to_xe_device(ttm_bo->bdev);
> > + struct iosys_map vmap;
> > + struct xe_res_cursor cursor;
> > + struct xe_mem_region *vram;
> > + void __iomem *virtual;
> > + int bytes_left = len;
> > +
> > + xe_bo_assert_held(bo);
>
> I think we need rpm somewhere? Although bo lock might make this tricky.
>
Do we? OFC if we interact with hardware we should but also if hardware
is powered off a BO shouldn't be in VRAM.
Maybe do a get_if_awake and bail otherwise?
Matt
> > +
> > + if (!mem_type_is_vram(ttm_bo->resource->mem_type))
> > + return -EIO;
> > +
> > + /* FIXME: Use GPU for non-visible VRAM */
> > + if (!(bo->flags & XE_BO_FLAG_NEEDS_CPU_ACCESS))
> > + return -EINVAL;
> > +
> > + vram = res_to_mem_region(ttm_bo->resource);
> > + xe_res_first(ttm_bo->resource, offset & ~PAGE_MASK, 0, &cursor);
> > +
> > + do {
> > + int wcount = PAGE_SIZE - (offset & PAGE_MASK) > bytes_left ?
> > + bytes_left : PAGE_SIZE - (offset & PAGE_MASK);
> > +
> > + virtual = (u8 __force *)vram->mapping + cursor.start;
> > +
> > + iosys_map_set_vaddr_iomem(&vmap, (void __iomem *)virtual);
> > + if (write)
> > + xe_map_memcpy_to(xe, &vmap, offset & PAGE_MASK, buf,
> > + wcount);
> > + else
> > + xe_map_memcpy_from(xe, buf, &vmap, offset & PAGE_MASK,
> > + wcount);
> > +
> > + offset += wcount;
> > + buf += wcount;
> > + bytes_left -= wcount;
> > + xe_res_next(&cursor, PAGE_SIZE);
> > + } while (bytes_left);
> > +
> > + return len;
> > +}
> > +
> > const struct ttm_device_funcs xe_ttm_funcs = {
> > .ttm_tt_create = xe_ttm_tt_create,
> > .ttm_tt_populate = xe_ttm_tt_populate,
> > @@ -1120,6 +1167,7 @@ const struct ttm_device_funcs xe_ttm_funcs = {
> > .move = xe_bo_move,
> > .io_mem_reserve = xe_ttm_io_mem_reserve,
> > .io_mem_pfn = xe_ttm_io_mem_pfn,
> > + .access_memory = xe_ttm_access_memory,
> > .release_notify = xe_ttm_bo_release_notify,
> > .eviction_valuable = ttm_bo_eviction_valuable,
> > .delete_mem_notify = xe_ttm_bo_delete_mem_notify,
> > diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
> > index 5804408815be..8ea11cd8df39 100644
> > --- a/include/drm/ttm/ttm_bo.h
> > +++ b/include/drm/ttm/ttm_bo.h
> > @@ -421,6 +421,8 @@ void ttm_bo_unpin(struct ttm_buffer_object *bo);
> > int ttm_bo_evict_first(struct ttm_device *bdev,
> > struct ttm_resource_manager *man,
> > struct ttm_operation_ctx *ctx);
> > +int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
> > + void *buf, int len, int write);
> > vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
> > struct vm_fault *vmf);
> > vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
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