[PATCH v3 10/10] drm/msm: Add a way for userspace to allocate GPU iova

Rob Clark
2022-04-06T21:52:32Z

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>
---
drivers/gpu/drm/msm/adreno/adreno_gpu.c | 10 ++++++
drivers/gpu/drm/msm/msm_drv.c | 21 +++++++++++
drivers/gpu/drm/msm/msm_gem.c | 48 +++++++++++++++++++++++++
drivers/gpu/drm/msm/msm_gem.h | 8 +++++
drivers/gpu/drm/msm/msm_gem_vma.c | 2 ++
include/uapi/drm/msm_drm.h | 3 ++
6 files changed, 92 insertions(+)

diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
index 6385ab06632f..4caae0229518 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
@@ -281,6 +281,16 @@ int adreno_get_param(struct msm_gpu *gpu, struct msm_file_private *ctx,
case MSM_PARAM_SUSPENDS:
*value = gpu->suspend_count;
return 0;
+ case MSM_PARAM_VA_START:
+ if (ctx->aspace == gpu->aspace)
+ return -EINVAL;
+ *value = ctx->aspace->va_start;
+ return 0;
+ case MSM_PARAM_VA_SIZE:
+ if (ctx->aspace == gpu->aspace)
+ return -EINVAL;
+ *value = ctx->aspace->va_size;
+ return 0;
default:
DBG("%s: invalid param: %u", gpu->name, param);
return -EINVAL;
diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index d618953d33ea..34e2169308b4 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -722,6 +722,23 @@ static int msm_ioctl_gem_info_iova(struct drm_device *dev,
return msm_gem_get_iova(obj, ctx->aspace, iova);
}

+static int msm_ioctl_gem_info_set_iova(struct drm_device *dev,
+ struct drm_file *file, struct drm_gem_object *obj,
+ uint64_t iova)
+{
+ struct msm_drm_private *priv = dev->dev_private;
+ struct msm_file_private *ctx = file->driver_priv;
+
+ if (!priv->gpu)
+ return -EINVAL;
+
+ /* Only supported if per-process address space is supported: */
+ if (priv->gpu->aspace == ctx->aspace)
+ return -EOPNOTSUPP;
+
+ return msm_gem_set_iova(obj, ctx->aspace, iova);
+}
+
static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
struct drm_file *file)
{
@@ -736,6 +753,7 @@ static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
switch (args->info) {
case MSM_INFO_GET_OFFSET:
case MSM_INFO_GET_IOVA:
+ case MSM_INFO_SET_IOVA:
/* value returned as immediate, not pointer, so len==0: */
if (args->len)
return -EINVAL;
@@ -760,6 +778,9 @@ static int msm_ioctl_gem_info(struct drm_device *dev, void *data,
case MSM_INFO_GET_IOVA:
ret = msm_ioctl_gem_info_iova(dev, file, obj, &args->value);
break;
+ case MSM_INFO_SET_IOVA:
+ ret = msm_ioctl_gem_info_set_iova(dev, file, obj, args->value);
+ break;
case MSM_INFO_SET_NAME:
/* length check should leave room for terminating null: */
if (args->len >= sizeof(msm_obj->name)) {
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index bf4af17e2f1e..3ee30b8a76bd 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -525,6 +525,54 @@ int msm_gem_get_iova(struct drm_gem_object *obj,
return ret;
}

+static int clear_iova(struct drm_gem_object *obj,
+ struct msm_gem_address_space *aspace)
+{
+ struct msm_gem_vma *vma = lookup_vma(obj, aspace);
+
+ if (!vma)
+ return 0;
+
+ if (msm_gem_vma_inuse(vma))
+ return -EBUSY;
+
+ msm_gem_purge_vma(vma->aspace, vma);
+ msm_gem_close_vma(vma->aspace, vma);
+ del_vma(vma);
+
+ return 0;
+}
+
+/*
+ * Get the requested iova but don't pin it. Fails if the requested iova is
+ * not available. Doesn't need a put because iovas are currently valid for
+ * the life of the object.
+ *
+ * Setting an iova of zero will clear the vma.
+ */
+int msm_gem_set_iova(struct drm_gem_object *obj,
+ struct msm_gem_address_space *aspace, uint64_t iova)
+{
+ int ret = 0;
+
+ msm_gem_lock(obj);
+ if (!iova) {
+ ret = clear_iova(obj, aspace);
+ } else {
+ struct msm_gem_vma *vma;
+ vma = get_vma_locked(obj, aspace, iova, iova + obj->size);
+ if (IS_ERR(vma)) {
+ ret = PTR_ERR(vma);
+ } else if (GEM_WARN_ON(vma->iova != iova)) {
+ clear_iova(obj, aspace);
+ ret = -EBUSY;
+ }
+ }
+ msm_gem_unlock(obj);
+
+ return ret;
+}
+
/*
* Unpin a iova by updating the reference counts. The memory isn't actually
* purged until something else (shrinker, mm_notifier, destroy, etc) decides
diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index 38d66e1248b1..efa2e5c19f1e 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -38,6 +38,12 @@ struct msm_gem_address_space {

/* @faults: the number of GPU hangs associated with this address space */
int faults;
+
+ /** @va_start: lowest possible address to allocate */
+ uint64_t va_start;
+
+ /** @va_size: the size of the address space (in bytes) */
+ uint64_t va_size;
};

struct msm_gem_address_space *
@@ -144,6 +150,8 @@ struct msm_gem_vma *msm_gem_get_vma_locked(struct drm_gem_object *obj,
struct msm_gem_address_space *aspace);
int msm_gem_get_iova(struct drm_gem_object *obj,
struct msm_gem_address_space *aspace, uint64_t *iova);
+int msm_gem_set_iova(struct drm_gem_object *obj,
+ struct msm_gem_address_space *aspace, uint64_t iova);
int msm_gem_get_and_pin_iova_range(struct drm_gem_object *obj,
struct msm_gem_address_space *aspace, uint64_t *iova,
u64 range_start, u64 range_end);
diff --git a/drivers/gpu/drm/msm/msm_gem_vma.c b/drivers/gpu/drm/msm/msm_gem_vma.c
index 6f9a402450f9..354f91aff573 100644
--- a/drivers/gpu/drm/msm/msm_gem_vma.c
+++ b/drivers/gpu/drm/msm/msm_gem_vma.c
@@ -182,6 +182,8 @@ 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);

diff --git a/include/uapi/drm/msm_drm.h b/include/uapi/drm/msm_drm.h
index 794ad1948497..3c7b097c4e3d 100644
--- a/include/uapi/drm/msm_drm.h
+++ b/include/uapi/drm/msm_drm.h
@@ -84,6 +84,8 @@ struct drm_msm_timespec {
#define MSM_PARAM_SYSPROF 0x0b /* WO: 1 preserves perfcntrs, 2 also disables suspend */
#define MSM_PARAM_COMM 0x0c /* WO: override for task->comm */
#define MSM_PARAM_CMDLINE 0x0d /* WO: override for task cmdline */
+#define MSM_PARAM_VA_START 0x0e /* RO: start of valid GPU iova range */
+#define MSM_PARAM_VA_SIZE 0x0f /* RO: size of valid GPU iova range (bytes) */

/* For backwards compat. The original support for preemption was based on
* a single ring per priority level so # of priority levels equals the #
@@ -135,6 +137,7 @@ struct drm_msm_gem_new {
#define MSM_INFO_GET_IOVA 0x01 /* get iova, returned by value */
#define MSM_INFO_SET_NAME 0x02 /* set the debug name (by pointer) */
#define MSM_INFO_GET_NAME 0x03 /* get debug name, returned by pointer */
+#define MSM_INFO_SET_IOVA 0x04 /* set the iova, passed by value */

struct drm_msm_gem_info {
__u32 handle; /* in */
--
2.35.1