virgl: Work around possible memory exhaustion

Since we don't normally flush before performing copy transfers, it's
possible in some scenarios to use too much memory for staging resources
and start failing. This can happen either because we exhaust the total
available memory (including system memory virtio-gpu swaps out to), or,
more commonly, because the total size of resources in a command buffer
doesn't fit in virtio-gpu video memory.

To reduce the chances of this happening, force a flush before a copy
transfer if the total size of queued staging resources exceeds a certain
limit. Since after a flush any queued staging resources will be
eventually released, this ensures both that each command buffer doesn't
require too much video memory, and that we don't end up consuming too
much memory for staging resources in total.

Fixes kernel errors reported when running texture_upload tests in glbench.

Signed-off-by: Alexandros Frantzis <[email protected]>
Reviewed-by: Chia-I Wu <[email protected]>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/gallium/drivers/virgl/virgl_context.c b/src/gallium/drivers/virgl/virgl_context.c
index 9964520d5e7..f1b35fd1257 100644
--- a/src/gallium/drivers/virgl/virgl_context.c
+++ b/src/gallium/drivers/virgl/virgl_context.c
@@ -778,6 +778,11 @@ static void virgl_flush_eq(struct virgl_context *ctx, void *closure,
    virgl_encoder_set_sub_ctx(ctx, ctx->hw_sub_ctx_id);
 
    ctx->cbuf_initial_cdw = ctx->cbuf->cdw;
+
+   /* We have flushed the command queue, including any pending copy transfers
+    * involving staging resources.
+    */
+   ctx->queued_staging_res_size = 0;
 }
 
 static void virgl_flush_from_st(struct pipe_context *ctx,