drm/msm: Add a way for userspace to allocate GPU iova

The motivation at this point is mainly native userspace mesa driver in a
VM guest.  The one remaining synchronous "hotpath" is buffer allocation,
because guest needs to wait to know the bo's iova before it can start
emitting cmdstream/state that references the new bo.  By allocating the
iova in the guest userspace, we no longer need to wait for a response
from the host, but can just rely on the allocation request being
processed before the cmdstream submission.  Allocation failures (OoM,
etc) would just be treated as context-lost (ie. GL_GUILTY_CONTEXT_RESET)
or subsequent allocations (or readpix, etc) can raise GL_OUT_OF_MEMORY.

v2: Fix inuse check
v3: Change mismatched iova case to -EBUSY

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://lore.kernel.org/r/20220411215849.297838-11-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/gpu/drm/msm/msm_gem_vma.c b/drivers/gpu/drm/msm/msm_gem_vma.c
index 0cd6770faf41..3c1dc9241831 100644
--- a/drivers/gpu/drm/msm/msm_gem_vma.c
+++ b/drivers/gpu/drm/msm/msm_gem_vma.c
@@ -184,6 +184,8 @@ msm_gem_address_space_create(struct msm_mmu *mmu, const char *name,
 	spin_lock_init(&aspace->lock);
 	aspace->name = name;
 	aspace->mmu = mmu;
+	aspace->va_start = va_start;
+	aspace->va_size  = size;
 
 	drm_mm_init(&aspace->mm, va_start, size);