On 03.03.21 14:20, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>
> There is no reason to disable pagefaults and preemption as a side effect of
> kmap_atomic_prot().
>
> Use kmap_local_page_prot() instead and document the reasoning for the
> mapping usage with the given pgprot.
>
> Remove the NULL pointer check for the map. These functions return a valid
> address for valid pages and the return was bogus anyway as it would have
> left preemption and pagefaults disabled.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: VMware Graphics <linux-graphics-maintainer@xxxxxxxxxx>
> Cc: Roland Scheidegger <sroland@xxxxxxxxxx>
> Cc: Zack Rusin <zackr@xxxxxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> ---
> drivers/gpu/drm/vmwgfx/vmwgfx_blit.c | 30 ++++++++++++------------------
> 1 file changed, 12 insertions(+), 18 deletions(-)
>
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_blit.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_blit.c
> @@ -375,12 +375,12 @@ static int vmw_bo_cpu_blit_line(struct v
> copy_size = min_t(u32, copy_size, PAGE_SIZE - src_page_offset);
>
> if (unmap_src) {
> - kunmap_atomic(d->src_addr);
> + kunmap_local(d->src_addr);
> d->src_addr = NULL;
> }
>
> if (unmap_dst) {
> - kunmap_atomic(d->dst_addr);
> + kunmap_local(d->dst_addr);
> d->dst_addr = NULL;
> }
>
> @@ -388,12 +388,8 @@ static int vmw_bo_cpu_blit_line(struct v
> if (WARN_ON_ONCE(dst_page >= d->dst_num_pages))
> return -EINVAL;
>
> - d->dst_addr =
> - kmap_atomic_prot(d->dst_pages[dst_page],
> - d->dst_prot);
> - if (!d->dst_addr)
> - return -ENOMEM;
> -
> + d->dst_addr = kmap_local_page_prot(d->dst_pages[dst_page],
> + d->dst_prot);
> d->mapped_dst = dst_page;
> }
>
> @@ -401,12 +397,8 @@ static int vmw_bo_cpu_blit_line(struct v
> if (WARN_ON_ONCE(src_page >= d->src_num_pages))
> return -EINVAL;
>
> - d->src_addr =
> - kmap_atomic_prot(d->src_pages[src_page],
> - d->src_prot);
> - if (!d->src_addr)
> - return -ENOMEM;
> -
> + d->src_addr = kmap_local_page_prot(d->src_pages[src_page],
> + d->src_prot);
> d->mapped_src = src_page;
> }
> diff->do_cpy(diff, d->dst_addr + dst_page_offset,
> @@ -436,8 +428,10 @@ static int vmw_bo_cpu_blit_line(struct v
> *
> * Performs a CPU blit from one buffer object to another avoiding a full
> * bo vmap which may exhaust- or fragment vmalloc space.
> - * On supported architectures (x86), we're using kmap_atomic which avoids
> - * cross-processor TLB- and cache flushes and may, on non-HIGHMEM systems
> + *
> + * On supported architectures (x86), we're using kmap_local_prot() which
> + * avoids cross-processor TLB- and cache flushes. kmap_local_prot() will
> + * either map a highmem page with the proper pgprot on HIGHMEM=y systems or
> * reference already set-up mappings.
> *
> * Neither of the buffer objects may be placed in PCI memory
> @@ -500,9 +494,9 @@ int vmw_bo_cpu_blit(struct ttm_buffer_ob
> }
> out:
> if (d.src_addr)
> - kunmap_atomic(d.src_addr);
> + kunmap_local(d.src_addr);
> if (d.dst_addr)
> - kunmap_atomic(d.dst_addr);
> + kunmap_local(d.dst_addr);
>
> return ret;
> }
>
>
Seems reasonable to me.
Reviewed-by: Roland Scheidegger <sroland@xxxxxxxxxx>
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