Quoting Tina Zhang (2017-10-16 09:57:33)
> GEM proxy is a kind of GEM whose backing physical memory is pinned
> and produced by guest VM and is used by host as read only. With GEM
> proxy, host is able to access guest physical memory through GEM object
> interface. As GEM proxy is such a special kind of GEM, a new flag
> I915_GEM_OBJECT_IS_PROXY is introduced to ban host from changing the
> backing storage of GEM proxy.
>
> V1:
> - the patch is separated from the "Dma-buf support for Gvt-g"
> patch-set. (Joonas)
>
> Here are the histories of this patch in "Dma-buf support for Gvt-g"
> patch-set:
>
> v14:
> - return -ENXIO when gem proxy object is banned by ioctl.
> (Chris) (Daniel)
>
> v13:
> - add comments to GEM proxy. (Chris)
> - don't ban GEM proxy in i915_gem_sw_finish_ioctl. (Chris)
> - check GEM proxy bar after finishing i915_gem_object_wait. (Chris)
> - remove GEM proxy bar in i915_gem_madvise_ioctl.
>
> v6:
> - add gem proxy barrier in the following ioctls. (Chris)
> i915_gem_set_caching_ioctl
> i915_gem_set_domain_ioctl
> i915_gem_sw_finish_ioctl
> i915_gem_set_tiling_ioctl
> i915_gem_madvise_ioctl
>
> Signed-off-by: Tina Zhang <tina.zhang@xxxxxxxxx>
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 22 ++++++++++++++++++++++
> drivers/gpu/drm/i915/i915_gem_object.h | 11 +++++++++--
> drivers/gpu/drm/i915/i915_gem_tiling.c | 8 ++++++++
> 3 files changed, 39 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 82a1003..7d3116a 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1593,6 +1593,16 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
> if (err)
> goto out;
>
> + /* Proxy objects do not control access to the backing storage, ergo
> + * they cannot be used as a means to manipulate the cache domain
> + * tracking for that backing storage. The proxy object is always
> + * considered to be outside of any cache domain.
> + */
> + if (i915_gem_object_is_proxy(obj)) {
> + err = -ENXIO;
> + goto out;
> + }
> +
> /* Flush and acquire obj->pages so that we are coherent through
> * direct access in memory with previous cached writes through
> * shmemfs and that our cache domain tracking remains valid.
> @@ -1649,6 +1659,10 @@ i915_gem_sw_finish_ioctl(struct drm_device *dev, void *data,
> if (!obj)
> return -ENOENT;
>
> + /* Proxy objects are barred from CPU access, so there is no
> + * need to ban sw_finish as it is a nop.
> + */
> +
Then we probably want a GEM_BUG_ON(i915_gem_object_is_proxy()) inside
pin_to_display and for this path, flush_if_display.
Otherwise, looking very nice. The comments are very much appreciated and
useful. I just need to go over the list of ioctls and check you have
everything.
-Chris
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