zink: allow software rendering only if selected

In environments where 3D acceleration is not available, like in a VM,
the behavior before commit 8cd44b884387 ("egl: add automatic zink
fallback loading between hw and sw drivers") was to fallback to swrast.

This was the output of `eglinfo` in that situation:

    $ eglinfo
    [...]
    Wayland platform:
    EGL driver name: swrast
    OpenGL core profile renderer: llvmpipe (LLVM 17.0.4, 256 bits)

However, after commit 8cd44b884387 ("egl: add automatic zink fallback
loading between hw and sw drivers") Zink support is tested before
falling back to swrast.
Since the system doesn't support 3D acceleration, Zink + software
rendering is used instead of swrast causing issues like the ones
described in #10146.

In this case, `eglinfo` prints:

    $ eglinfo
    [...]
    Wayland platform:
    EGL driver name: zink
    OpenGL core profile renderer: zink Vulkan 1.3(llvmpipe (LLVM 17.0.4,
    256 bits) (MESA_LLVMPIPE))

This patch ensures that Zink + software rendering is used only when the
user opts-in by setting `LIBGL_ALWAYS_SOFTWARE` or `D3D_ALWAYS_SOFTWARE`
and swrast is used otherwise.

After the patch, the output of `eglinfo` is identical to the one before
the regression:

    $ eglinfo
    [...]
    Wayland platform:
    EGL driver name: swrast
    OpenGL core profile renderer: llvmpipe (LLVM 17.0.4, 256 bits)

Resolves: https://gitlab.freedesktop.org/mesa/mesa/-/issues/10146
Fixes: 8cd44b884387 ("egl: add automatic zink fallback loading between
hw and sw drivers")

Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Signed-off-by: José Expósito <jexposit@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26220>
(cherry picked from commit 2a71f06f2938678d89d5ed1372cda6a7b55d964d)

diff --git a/.pick_status.json b/.pick_status.json
index 6640f34..8a0c109 100644 (file)
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -1244,7 +1244,7 @@
         "description": "zink: allow software rendering only if selected",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "8cd44b8843877a2f7d559d123eb3694841f16fdc",
         "notes": null

diff --git a/src/gallium/drivers/zink/zink_screen.c b/src/gallium/drivers/zink/zink_screen.c
index 29a377a..50168d8 100644 (file)
--- a/src/gallium/drivers/zink/zink_screen.c
+++ b/src/gallium/drivers/zink/zink_screen.c
@@ -1632,6 +1632,12 @@ choose_pdev(struct zink_screen *screen, int64_t dev_major, int64_t dev_minor)
    }
    VKSCR(GetPhysicalDeviceProperties)(screen->pdev, &screen->info.props);
 
+   /* allow software rendering only if forced by the user */
+   if (!cpu && screen->info.props.deviceType == VK_PHYSICAL_DEVICE_TYPE_CPU) {
+      screen->pdev = VK_NULL_HANDLE;
+      return;
+   }
+
    screen->info.device_version = screen->info.props.apiVersion;
 
    /* runtime version is the lesser of the instance version and device version */