devices: gpu: add support for mesa gpu shader cache

When requested with the --gpu=cache-path=/path arg, crosvm
will pass it to Mesa via env var MESA_GLSL_CACHE_DIR. In
addition, the cache-size will also be passed along if
provided.

BUG=b:168540438
TEST=run with --gpu=cache-path=/tmp,cache-size=50M and
 confirm that files are created in /tmp/mesa_shader_cache.

Change-Id: I2525597749d654a65373a723cefeab6cf2be62d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2415509
Tested-by: John Bates <jbates@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: David Riley <davidriley@chromium.org>

devices/src/virtio/gpu/mod.rs

@@ -76,6 +76,8 @@ pub struct GpuParameters {
     #[cfg(feature = "gfxstream")]
     pub gfxstream_support_vulkan: bool,
     pub mode: GpuMode,
+    pub cache_path: Option<String>,
+    pub cache_size: Option<String>,
 }
 
 // First queue is for virtio gpu commands. Second queue is for cursor commands, which we expect
@@ -101,6 +103,8 @@ impl Default for GpuParameters {
             #[cfg(feature = "gfxstream")]
             gfxstream_support_vulkan: true,
             mode: GpuMode::Mode3D,
+            cache_path: None,
+            cache_size: None,
         }
     }
 }

seccomp/x86_64/gpu_device.policy

@@ -71,6 +71,14 @@ stat: 1
 statx: 1
 sysinfo: 1
 
+# Rules for Mesa's shader binary cache.
+flock: 1
+mkdir: 1
+newfstatat: 1
+rename: 1
+setpriority: 1
+unlink: 1
+
 # Rules specific to AMD gpus.
 uname: 1
 sched_setscheduler: 1

src/linux.rs

@@ -4,6 +4,8 @@
 
 use std::cmp::{max, Reverse};
 use std::convert::TryFrom;
+#[cfg(feature = "gpu")]
+use std::env;
 use std::error::Error as StdError;
 use std::ffi::CStr;
 use std::fmt::{self, Display};
@@ -736,6 +738,29 @@ fn create_gpu_device(
                 jail.mount_bind(drm_dri_path, drm_dri_path, false)?;
             }
 
+            // Prepare GPU shader disk cache directory.
+            if let Some(cache_dir) = cfg
+                .gpu_parameters
+                .as_ref()
+                .and_then(|params| params.cache_path.as_ref())
+            {
+                if cfg!(any(target_arch = "arm", target_arch = "aarch64")) && cfg.sandbox {
+                    warn!("shader caching not yet supported on ARM with sandbox enabled");
+                    env::set_var("MESA_GLSL_CACHE_DISABLE", "true");
+                } else {
+                    env::set_var("MESA_GLSL_CACHE_DIR", cache_dir);
+                    if let Some(cache_size) = cfg
+                        .gpu_parameters
+                        .as_ref()
+                        .and_then(|params| params.cache_size.as_ref())
+                    {
+                        env::set_var("MESA_GLSL_CACHE_MAX_SIZE", cache_size);
+                    }
+                    let shadercache_path = Path::new(cache_dir);
+                    jail.mount_bind(shadercache_path, shadercache_path, true)?;
+                }
+            }
+
             // If the ARM specific devices exist on the host, bind mount them in.
             let mali0_path = Path::new("/dev/mali0");
             if mali0_path.exists() {

src/main.rs

@@ -322,6 +322,8 @@ fn parse_gpu_options(s: Option<&str>) -> argument::Result<GpuParameters> {
                                 ),
                             })?;
                 }
+                "cache-path" => gpu_params.cache_path = Some(v.to_string()),
+                "cache-size" => gpu_params.cache_size = Some(v.to_string()),
                 "" => {}
                 _ => {
                     return Err(argument::Error::UnknownArgument(format!(