Currently, NO_PREFETCH is passed implicitly through
drm_nouveau_gem_pushbuf_push::length and drm_nouveau_exec_push::va_len.

Since this is a direct representation of how the HW is programmed it
isn't really future proof for a uAPI. Hence, fix this up for the new
uAPI and split up the va_len field of struct drm_nouveau_exec_push,
such that we keep 32bit for va_len and 32bit for flags.

For drm_nouveau_gem_pushbuf_push::length at least provide
NOUVEAU_GEM_PUSHBUF_NO_PREFETCH to indicate the bit shift.

While at it, fix up nv50_dma_push() as well, such that the caller
doesn't need to encode the NO_PREFETCH flag into the length parameter.

Signed-off-by: Danilo Krummrich <dakr@redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_dma.c  |  7 +++++--
 drivers/gpu/drm/nouveau/nouveau_dma.h  |  8 ++++++--
 drivers/gpu/drm/nouveau/nouveau_exec.c | 15 ++++++++++++---
 drivers/gpu/drm/nouveau/nouveau_gem.c  |  6 ++++--
 include/uapi/drm/nouveau_drm.h         |  8 +++++++-
 5 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dma.c b/drivers/gpu/drm/nouveau/nouveau_dma.c
index b90cac6d5772..059925e5db6a 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dma.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dma.c
@@ -69,16 +69,19 @@ READ_GET(struct nouveau_channel *chan, uint64_t *prev_get, int *timeout)
 }
 
 void
-nv50_dma_push(struct nouveau_channel *chan, u64 offset, int length)
+nv50_dma_push(struct nouveau_channel *chan, u64 offset, u32 length,
+	      bool prefetch)
 {
 	struct nvif_user *user = &chan->drm->client.device.user;
 	struct nouveau_bo *pb = chan->push.buffer;
 	int ip = (chan->dma.ib_put * 2) + chan->dma.ib_base;
 
 	BUG_ON(chan->dma.ib_free < 1);
+	WARN_ON(length > NV50_DMA_PUSH_MAX_LENGTH);
 
 	nouveau_bo_wr32(pb, ip++, lower_32_bits(offset));
-	nouveau_bo_wr32(pb, ip++, upper_32_bits(offset) | length << 8);
+	nouveau_bo_wr32(pb, ip++, upper_32_bits(offset) | length << 8 |
+			(prefetch ? 0 : (1 << 31)));
 
 	chan->dma.ib_put = (chan->dma.ib_put + 1) & chan->dma.ib_max;
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_dma.h b/drivers/gpu/drm/nouveau/nouveau_dma.h
index 035a709c7be1..fb471c357336 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dma.h
+++ b/drivers/gpu/drm/nouveau/nouveau_dma.h
@@ -31,7 +31,8 @@
 #include "nouveau_chan.h"
 
 int nouveau_dma_wait(struct nouveau_channel *, int slots, int size);
-void nv50_dma_push(struct nouveau_channel *, u64 addr, int length);
+void nv50_dma_push(struct nouveau_channel *, u64 addr, u32 length,
+		   bool prefetch);
 
 /*
  * There's a hw race condition where you can't jump to your PUT offset,
@@ -45,6 +46,9 @@ void nv50_dma_push(struct nouveau_channel *, u64 addr, int length);
  */
 #define NOUVEAU_DMA_SKIPS (128 / 4)
 
+/* Maximum push buffer size. */
+#define NV50_DMA_PUSH_MAX_LENGTH 0x7fffff
+
 /* Object handles - for stuff that's doesn't use handle == oclass. */
 enum {
 	NvDmaFB		= 0x80000002,
@@ -89,7 +93,7 @@ FIRE_RING(struct nouveau_channel *chan)
 
 	if (chan->dma.ib_max) {
 		nv50_dma_push(chan, chan->push.addr + (chan->dma.put << 2),
-			      (chan->dma.cur - chan->dma.put) << 2);
+			      (chan->dma.cur - chan->dma.put) << 2, true);
 	} else {
 		WRITE_PUT(chan->dma.cur);
 	}
diff --git a/drivers/gpu/drm/nouveau/nouveau_exec.c b/drivers/gpu/drm/nouveau/nouveau_exec.c
index 0f927adda4ed..a123b07b2adf 100644
--- a/drivers/gpu/drm/nouveau/nouveau_exec.c
+++ b/drivers/gpu/drm/nouveau/nouveau_exec.c
@@ -164,8 +164,10 @@ nouveau_exec_job_run(struct nouveau_job *job)
 	}
 
 	for (i = 0; i < exec_job->push.count; i++) {
-		nv50_dma_push(chan, exec_job->push.s[i].va,
-			      exec_job->push.s[i].va_len);
+		struct drm_nouveau_exec_push *p = &exec_job->push.s[i];
+		bool prefetch = !(p->flags & DRM_NOUVEAU_EXEC_PUSH_NO_PREFETCH);
+
+		nv50_dma_push(chan, p->va, p->va_len, prefetch);
 	}
 
 	ret = nouveau_fence_emit(fence, chan);
@@ -223,7 +225,14 @@ nouveau_exec_job_init(struct nouveau_exec_job **pjob,
 {
 	struct nouveau_exec_job *job;
 	struct nouveau_job_args args = {};
-	int ret;
+	int i, ret;
+
+	for (i = 0; i < __args->push.count; i++) {
+		struct drm_nouveau_exec_push *p = &__args->push.s[i];
+
+		if (p->va_len > NV50_DMA_PUSH_MAX_LENGTH)
+			return -EINVAL;
+	}
 
 	job = *pjob = kzalloc(sizeof(*job), GFP_KERNEL);
 	if (!job)
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index f39360870c70..2f3dc4d71657 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -856,9 +856,11 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void *data,
 		for (i = 0; i < req->nr_push; i++) {
 			struct nouveau_vma *vma = (void *)(unsigned long)
 				bo[push[i].bo_index].user_priv;
+			u64 addr = vma->addr + push[i].offset;
+			u32 length = push[i].length & ~NOUVEAU_GEM_PUSHBUF_NO_PREFETCH;
+			bool prefetch = !(push[i].length & NOUVEAU_GEM_PUSHBUF_NO_PREFETCH);
 
-			nv50_dma_push(chan, vma->addr + push[i].offset,
-				      push[i].length);
+			nv50_dma_push(chan, addr, length, prefetch);
 		}
 	} else
 	if (drm->client.device.info.chipset >= 0x25) {
diff --git a/include/uapi/drm/nouveau_drm.h b/include/uapi/drm/nouveau_drm.h
index b1ad9d5ffce8..8f16724b5d05 100644
--- a/include/uapi/drm/nouveau_drm.h
+++ b/include/uapi/drm/nouveau_drm.h
@@ -138,6 +138,7 @@ struct drm_nouveau_gem_pushbuf_push {
 	__u32 pad;
 	__u64 offset;
 	__u64 length;
+#define NOUVEAU_GEM_PUSHBUF_NO_PREFETCH (1 << 23)
 };
 
 struct drm_nouveau_gem_pushbuf {
@@ -338,7 +339,12 @@ struct drm_nouveau_exec_push {
 	/**
 	 * @va_len: the length of the push buffer mapping
 	 */
-	__u64 va_len;
+	__u32 va_len;
+	/**
+	 * flags: the flags for this push buffer mapping
+	 */
+	__u32 flags;
+#define DRM_NOUVEAU_EXEC_PUSH_NO_PREFETCH 0x1
 };
 
 /**

base-commit: ad1367f831f8743746a1f49705c28e36a7c95525
-- 
2.41.0

Hi Danilo,

kernel test robot noticed the following build warnings:

[auto build test WARNING on ad1367f831f8743746a1f49705c28e36a7c95525]

url:    https://github.com/intel-lab-lkp/linux/commits/Danilo-Krummrich/drm-nouveau-uapi-don-t-pass-NO_PREFETCH-flag-implicitly/20230823-074237
base:   ad1367f831f8743746a1f49705c28e36a7c95525
patch link:    https://lore.kernel.org/r/20230822234139.11185-1-dakr%40redhat.com
patch subject: [PATCH drm-misc-next] drm/nouveau: uapi: don't pass NO_PREFETCH flag implicitly
reproduce: (https://download.01.org/0day-ci/archive/20230823/202308232030.0r1irPMu-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202308232030.0r1irPMu-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> ./include/uapi/drm/nouveau_drm.h:344: warning: Incorrect use of kernel-doc format:          * flags: the flags for this push buffer mapping
>> ./include/uapi/drm/nouveau_drm.h:348: warning: Function parameter or member 'flags' not described in 'drm_nouveau_exec_push'

vim +344 ./include/uapi/drm/nouveau_drm.h

   327	
   328	/**
   329	 * struct drm_nouveau_exec_push - EXEC push operation
   330	 *
   331	 * This structure represents a single EXEC push operation. UMDs should pass an
   332	 * array of this structure via struct drm_nouveau_exec's &push_ptr field.
   333	 */
   334	struct drm_nouveau_exec_push {
   335		/**
   336		 * @va: the virtual address of the push buffer mapping
   337		 */
   338		__u64 va;
   339		/**
   340		 * @va_len: the length of the push buffer mapping
   341		 */
   342		__u32 va_len;
   343		/**
 > 344		 * flags: the flags for this push buffer mapping
   345		 */
   346		__u32 flags;
   347	#define DRM_NOUVEAU_EXEC_PUSH_NO_PREFETCH 0x1
 > 348	};
   349	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki