virgl: Fake MSAA when max samples is 1

When the host is running on softpipe/llvmpipe the maximum number of
samples for multisampling is 1. GL 3.0 requires at least 4 samples, and
softpipe/llvmpipe get around this by enabling PIPE_CAP_FAKE_SW_MSAA.

This patch mimics softpipe/llvmpipe behavior in virgl by enabling the
same PIPE_CAP_FAKE_SW_MSAA workaround when the max sample count reported
by the host is 1. This change allows virgl on a softpipe/llvmpipe host
to advertise support for GL 3.0 and beyond.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-By: Gert Wollny <gert.wollny@collabora.com>

diff --git a/src/gallium/drivers/virgl/virgl_screen.c b/src/gallium/drivers/virgl/virgl_screen.c
index 66e520eab8a09a00f6800484b75d88efbb2ccd8f..1ad8863bfca6c4a1e07fca9094810b33923d2b4f 100644 (file)
--- a/src/gallium/drivers/virgl/virgl_screen.c
+++ b/src/gallium/drivers/virgl/virgl_screen.c
@@ -265,9 +265,12 @@ virgl_get_param(struct pipe_screen *screen, enum pipe_cap param)
       if (vscreen->caps.caps.v1.glsl_level < 150)
          return vscreen->caps.caps.v2.max_vertex_attribs;
       return 32;
+   case PIPE_CAP_FAKE_SW_MSAA:
+      /* If the host supports only one sample (e.g., if it is using softpipe),
+       * fake multisampling to able to advertise higher GL versions. */
+      return (vscreen->caps.caps.v1.max_samples == 1) ? 1 : 0;
    case PIPE_CAP_TEXTURE_GATHER_SM5:
    case PIPE_CAP_BUFFER_MAP_PERSISTENT_COHERENT:
-   case PIPE_CAP_FAKE_SW_MSAA:
    case PIPE_CAP_TEXTURE_GATHER_OFFSETS:
    case PIPE_CAP_TGSI_VS_WINDOW_SPACE_POSITION:
    case PIPE_CAP_MULTI_DRAW_INDIRECT: