On Saturday, April 22, 2017 3:55:07 PM PDT Jason Ekstrand wrote: > This fixes rendering corruptions in DOOM. Hopefully, it will also make > Jenkins a bit more stable as we've been seeing some random failures and > GPU hangs ever since turning on 48bit. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100620 > Cc: "17.1" <mesa-sta...@lists.freedesktop.org> > --- > src/intel/vulkan/anv_allocator.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/src/intel/vulkan/anv_allocator.c > b/src/intel/vulkan/anv_allocator.c > index 78327df..28bfac4 100644 > --- a/src/intel/vulkan/anv_allocator.c > +++ b/src/intel/vulkan/anv_allocator.c > @@ -994,6 +994,22 @@ anv_scratch_pool_alloc(struct anv_device *device, struct > anv_scratch_pool *pool, > > anv_bo_init_new(&bo->bo, device, size); > > + /* Even though the Scratch base pointers in 3DSTATE_*S are 64 bits, they > + * are still relative to the general state base address. When we emit > + * STATE_BASE_ADDRESS, we set general state base address to 0 and the size > + * to the maximum (1 page under 4GB). This allows us to just place the > + * scratch buffers anywhere we wish in the bottom 32 bits of address space > + * and just set the scratch base pointer in 3DSTATE_*S using a relocation. > + * However, in order to do so, we need to ensure that the kernel does not > + * place the scratch BO above the 32-bit boundary. > + * > + * NOTE: Technically, it can't go "anywhere" because the top page is off > + * limits. However, it will never end up getting placed that high because > + * the surface state and general state buffers will get placed first and > + * the kernel likes to work top-down.
This NOTE sounds unnecessarily scary.
If you don't set EXEC_OBJECT_SUPPORTS_48B_ADDRESS, then the kernel sets
this to PIN_ZONE_4G...which in i915_vma.c does:
end = min_t(u64, end, (1ULL << 32) - I915_GTT_PAGE_SIZE);
If I'm reading the kernel code correctly, that means the kernel is
explicitly refusing to position it in that top page. So it's not a
side effect of the kernel "liking to work top-down" - I'm pretty sure
it works by design, not by accident.
Reviewed-by: Kenneth Graunke <kenn...@whitecape.org>
> + */
> + bo->bo.flags &= ~EXEC_OBJECT_SUPPORTS_48B_ADDRESS;
> +
> /* Set the exists last because it may be read by other threads */
> __sync_synchronize();
> bo->exists = true;
>
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