[Mesa-dev] [PATCH] virgl: Allow RGB32* textures only as buffer objects

[Gert Wollny]

Am Sonntag, den 22.07.2018, 09:59 -0400 schrieb Ilia Mirkin:
> On Sun, Jul 22, 2018 at 2:54 AM, Gert Wollny <gert.wollny at collabora.c
> om> wrote:
> > Am Samstag, den 21.07.2018, 14:14 -0400 schrieb Ilia Mirkin:
> > > On Sat, Jul 21, 2018 at 1:48 PM, Gert Wollny <gert.wollny at collabo
> > > ra.c
> > > om> wrote:
> > > > Am Samstag, den 21.07.2018, 11:33 -0400 schrieb Ilia Mirkin:
> > > > > 
> > > > > 
> > > > > On Sat, Jul 21, 2018, 05:45 Gert Wollny <gert.wollny at collabor
> > > > > a.co
> > > > > m>
> > > > > wrote:
> > > > > > Am Freitag, den 20.07.2018, 12:31 -0400 schrieb Ilia
> > > > > > Mirkin:
> > > > > > > 
> > > > > > > > +   /* Allow 3-comp 32 bit texturs only for TBOs
> > > > > > > > (needed
> > > > > > > > for
> > > > > > > > ARB_tbo_rgb32) */
> > > > > > > > +   if ((format == PIPE_FORMAT_R32G32B32_FLOAT ||
> > > > > > > > +       format == PIPE_FORMAT_R32G32B32_SINT ||
> > > > > > > > +       format == PIPE_FORMAT_R32G32B32_UINT) &&
> > > > > > > > +       target != PIPE_BUFFER)
> > > > > > > > +      return FALSE;
> > > > > > > 
> > > > > > > My personal recommendation would be to disallow *all*
> > > > > > > packed
> > > > > > > RGB
> > > > > > > formats unless target == PIPE_BUFFER. (And even then --
> > > > > > 
> > > > > > questionable,
> > > > > > > except for RGB32, which is required.)
> > > > > > > 
> > > > > > 
> > > > > > RGB8 and RGB16 are disabled/replaced by RGBX* on the host
> > > > > > side,
> > > > > > and
> > > > > > R11G11B10 doesn't seem to make problems.
> > > > > 
> > > > > No other driver supports these. What happens on the host side
> > > > > is
> > > > > hidden from virgl.
> > > > 
> > > > Not exactly, of course the host tells virgl what formats are
> > > > supported,
> > > > and we test using dEQP and piglit quite heavily to get things
> > > > right, so
> > > > I'm quite confident that whatever problem comes up, we will
> > > > catch
> > > > it.
> > > 
> > > The result is that you end up lying to mesa and the various
> > > helpers
> > > --
> > > the user creates a RGB8 texture, which your gallium driver claims
> > > to
> > > support. In reality, it's a RGBX texture on the host, but this
> > > information is hidden from virgl
> > 
> > No, it is not, virgl_is_format_supported will not claim that the
> > RGB format is supported, it will pick PIPE_FORMAT_RnGnBnXn_* also
> > on the guest side, because PIPE_FORMAT_RnGnBn_* (n = 8,16) is not
> > in the list of driver supported formats (not even for buffers),
> > this information is in the caps sampler.bitmask and render.bitmask
> > that are send from the host and that are also checked in this
> > function. Only because we can not remove  PIPE_FORMAT_R32G32B32_*
> > completely we need this additional check.
> 
> So to confirm, is_format_supported(PIPE_FORMAT_R8G8B8_UNORM) will
> return false, irrespective of what the host driver might be. Correct?
Yes 

best. 
Gert