[PATCH v3 09/10] drm/msm/gem: Add fenced vma unpin

Rob Clark
2022-04-06T21:52:04Z

With userspace allocated iova (next patch), we can have a race condition
where userspace observes the fence completion and deletes the vma before
retire_submit() gets around to unpinning the vma. To handle this, add a
fenced unpin which drops the refcount but tracks the fence, and update
msm_gem_vma_inuse() to check any previously unsignaled fences.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
drivers/gpu/drm/msm/msm_fence.c | 6 ++++--
drivers/gpu/drm/msm/msm_fence.h | 3 +++
drivers/gpu/drm/msm/msm_gem.c | 2 +-
drivers/gpu/drm/msm/msm_gem.h | 9 +++++++--
drivers/gpu/drm/msm/msm_gem_vma.c | 28 +++++++++++++++++++++++++---
drivers/gpu/drm/msm/msm_ringbuffer.c | 12 +++++++++++-
6 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_fence.c b/drivers/gpu/drm/msm/msm_fence.c
index f2cece542c3f..3df255402a33 100644
--- a/drivers/gpu/drm/msm/msm_fence.c
+++ b/drivers/gpu/drm/msm/msm_fence.c
@@ -15,6 +15,7 @@ msm_fence_context_alloc(struct drm_device *dev, volatile uint32_t *fenceptr,
const char *name)
{
struct msm_fence_context *fctx;
+ static int index = 0;

fctx = kzalloc(sizeof(*fctx), GFP_KERNEL);
if (!fctx)
@@ -23,6 +24,7 @@ msm_fence_context_alloc(struct drm_device *dev, volatile uint32_t *fenceptr,
fctx->dev = dev;
strncpy(fctx->name, name, sizeof(fctx->name));
fctx->context = dma_fence_context_alloc(1);
+ fctx->index = index++;
fctx->fenceptr = fenceptr;
spin_lock_init(&fctx->spinlock);

@@ -34,7 +36,7 @@ void msm_fence_context_free(struct msm_fence_context *fctx)
kfree(fctx);
}

-static inline bool fence_completed(struct msm_fence_context *fctx, uint32_t fence)
+bool msm_fence_completed(struct msm_fence_context *fctx, uint32_t fence)
{
/*
* Note: Check completed_fence first, as fenceptr is in a write-combine
@@ -76,7 +78,7 @@ static const char *msm_fence_get_timeline_name(struct dma_fence *fence)
static bool msm_fence_signaled(struct dma_fence *fence)
{
struct msm_fence *f = to_msm_fence(fence);
- return fence_completed(f->fctx, f->base.seqno);
+ return msm_fence_completed(f->fctx, f->base.seqno);
}

static const struct dma_fence_ops msm_fence_ops = {
diff --git a/drivers/gpu/drm/msm/msm_fence.h b/drivers/gpu/drm/msm/msm_fence.h
index 17ee3822b423..7f1798c54cd1 100644
--- a/drivers/gpu/drm/msm/msm_fence.h
+++ b/drivers/gpu/drm/msm/msm_fence.h
@@ -21,6 +21,8 @@ struct msm_fence_context {
char name[32];
/** context: see dma_fence_context_alloc() */
unsigned context;
+ /** index: similar to context, but local to msm_fence_context's */
+ unsigned index;

/**
* last_fence:
@@ -56,6 +58,7 @@ struct msm_fence_context * msm_fence_context_alloc(struct drm_device *dev,
volatile uint32_t *fenceptr, const char *name);
void msm_fence_context_free(struct msm_fence_context *fctx);

+bool msm_fence_completed(struct msm_fence_context *fctx, uint32_t fence);
void msm_update_fence(struct msm_fence_context *fctx, uint32_t fence);

struct dma_fence * msm_fence_alloc(struct msm_fence_context *fctx);
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index e8107a22c33a..bf4af17e2f1e 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -445,7 +445,7 @@ void msm_gem_unpin_vma_locked(struct drm_gem_object *obj, struct msm_gem_vma *vm

GEM_WARN_ON(!msm_gem_is_locked(obj));

- msm_gem_unmap_vma(vma->aspace, vma);
+ msm_gem_unpin_vma(vma);

msm_obj->pin_count--;
GEM_WARN_ON(msm_obj->pin_count < 0);
diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index f98264cf130d..38d66e1248b1 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -49,6 +49,8 @@ struct msm_gem_address_space *
msm_gem_address_space_create(struct msm_mmu *mmu, const char *name,
u64 va_start, u64 size);

+struct msm_fence_context;
+
struct msm_gem_vma {
struct drm_mm_node node;
uint64_t iova;
@@ -56,6 +58,9 @@ struct msm_gem_vma {
struct list_head list; /* node in msm_gem_object::vmas */
bool mapped;
int inuse;
+ uint32_t fence_mask;
+ uint32_t fence[MSM_GPU_MAX_RINGS];
+ struct msm_fence_context *fctx[MSM_GPU_MAX_RINGS];
};

int msm_gem_init_vma(struct msm_gem_address_space *aspace,
@@ -64,8 +69,8 @@ int msm_gem_init_vma(struct msm_gem_address_space *aspace,
bool msm_gem_vma_inuse(struct msm_gem_vma *vma);
void msm_gem_purge_vma(struct msm_gem_address_space *aspace,
struct msm_gem_vma *vma);
-void msm_gem_unmap_vma(struct msm_gem_address_space *aspace,
- struct msm_gem_vma *vma);
+void msm_gem_unpin_vma(struct msm_gem_vma *vma);
+void msm_gem_unpin_vma_fenced(struct msm_gem_vma *vma, struct msm_fence_context *fctx);
int msm_gem_map_vma(struct msm_gem_address_space *aspace,
struct msm_gem_vma *vma, int prot,
struct sg_table *sgt, int size);
diff --git a/drivers/gpu/drm/msm/msm_gem_vma.c b/drivers/gpu/drm/msm/msm_gem_vma.c
index 4949899f1fc7..6f9a402450f9 100644
--- a/drivers/gpu/drm/msm/msm_gem_vma.c
+++ b/drivers/gpu/drm/msm/msm_gem_vma.c
@@ -5,6 +5,7 @@
*/

#include "msm_drv.h"
+#include "msm_fence.h"
#include "msm_gem.h"
#include "msm_mmu.h"

@@ -39,7 +40,19 @@ msm_gem_address_space_get(struct msm_gem_address_space *aspace)

bool msm_gem_vma_inuse(struct msm_gem_vma *vma)
{
- return !!vma->inuse;
+ if (vma->inuse > 0)
+ return true;
+
+ while (vma->fence_mask) {
+ unsigned idx = ffs(vma->fence_mask) - 1;
+
+ if (!msm_fence_completed(vma->fctx[idx], vma->fence[idx]))
+ return true;
+
+ vma->fence_mask &= ~BIT(idx);
+ }
+
+ return false;
}

/* Actually unmap memory for the vma */
@@ -63,13 +76,22 @@ void msm_gem_purge_vma(struct msm_gem_address_space *aspace,
}

/* Remove reference counts for the mapping */
-void msm_gem_unmap_vma(struct msm_gem_address_space *aspace,
- struct msm_gem_vma *vma)
+void msm_gem_unpin_vma(struct msm_gem_vma *vma)
{
if (!GEM_WARN_ON(!vma->iova))
vma->inuse--;
}

+/* Replace pin reference with fence: */
+void msm_gem_unpin_vma_fenced(struct msm_gem_vma *vma, struct msm_fence_context *fctx)
+{
+ vma->fctx[fctx->index] = fctx;
+ vma->fence[fctx->index] = fctx->last_fence;
+ vma->fence_mask |= BIT(fctx->index);
+ msm_gem_unpin_vma(vma);
+}
+
+/* Map and pin vma: */
int
msm_gem_map_vma(struct msm_gem_address_space *aspace,
struct msm_gem_vma *vma, int prot,
diff --git a/drivers/gpu/drm/msm/msm_ringbuffer.c b/drivers/gpu/drm/msm/msm_ringbuffer.c
index 367a6aaa3a20..4ab5448fe070 100644
--- a/drivers/gpu/drm/msm/msm_ringbuffer.c
+++ b/drivers/gpu/drm/msm/msm_ringbuffer.c
@@ -14,9 +14,19 @@ module_param(num_hw_submissions, uint, 0600);
static struct dma_fence *msm_job_run(struct drm_sched_job *job)
{
struct msm_gem_submit *submit = to_msm_submit(job);
+ struct msm_fence_context *fctx = submit->ring->fctx;
struct msm_gpu *gpu = submit->gpu;
+ int i;

- submit->hw_fence = msm_fence_alloc(submit->ring->fctx);
+ submit->hw_fence = msm_fence_alloc(fctx);
+
+ for (i = 0; i < submit->nr_bos; i++) {
+ struct drm_gem_object *obj = &submit->bos[i].obj->base;
+
+ msm_gem_lock(obj);
+ msm_gem_unpin_vma_fenced(submit->bos[i].vma, fctx);
+ msm_gem_unlock(obj);
+ }

pm_runtime_get_sync(&gpu->pdev->dev);

--
2.35.1