Re: [PATCH 2/3] drm/nouveau: slowpath for pushbuf ioctl

From: Daniel Vetter <daniel-/w4YWyX8dFk@public.gmane.org>
To: DRI Development
	<dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>
Cc: nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
	Intel Graphics Development
	<intel-gfx-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org>,
	Ben Skeggs <bskeggs-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Daniel Vetter
	<daniel.vetter-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 2/3] drm/nouveau: slowpath for pushbuf ioctl
Date: Wed, 18 Sep 2019 11:29:47 +0200	[thread overview]
Message-ID: <20190918092947.GE3958@phenom.ffwll.local> (raw)
In-Reply-To: <20190903081714.GO2112-dv86pmgwkMBes7Z6vYuT8azUEOm+Xw19@public.gmane.org>

On Tue, Sep 03, 2019 at 10:17:14AM +0200, Daniel Vetter wrote:
> On Wed, Aug 21, 2019 at 11:50:29PM +0200, Daniel Vetter wrote:
> > We can't copy_*_user while holding reservations, that will (soon even
> > for nouveau) lead to deadlocks. And it breaks the cross-driver
> > contract around dma_resv.
> > 
> > Fix this by adding a slowpath for when we need relocations, and by
> > pushing the writeback of the new presumed offsets to the very end.
> > 
> > Aside from "it compiles" entirely untested unfortunately.
> > 
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ben Skeggs <bskeggs@redhat.com>
> > Cc: nouveau@lists.freedesktop.org
> 
> Ping for some review/testing (apparently needs pre-nv50). I'd really like
> to land this series here, it should help a lot in making sure everyone
> uses dma_resv in a compatible way across drivers.

Now that the gem/ttm fallout is fixed, ping for testing on this one here
... Also need some r-b to get this landed.

Thanks, Daniel

> > ---
> >  drivers/gpu/drm/nouveau/nouveau_gem.c | 57 ++++++++++++++++++---------
> >  1 file changed, 38 insertions(+), 19 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
> > index c77302f969e8..60309b997951 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> > @@ -482,12 +482,9 @@ validate_init(struct nouveau_channel *chan, struct drm_file *file_priv,
> >  
> >  static int
> >  validate_list(struct nouveau_channel *chan, struct nouveau_cli *cli,
> > -	      struct list_head *list, struct drm_nouveau_gem_pushbuf_bo *pbbo,
> > -	      uint64_t user_pbbo_ptr)
> > +	      struct list_head *list, struct drm_nouveau_gem_pushbuf_bo *pbbo)
> >  {
> >  	struct nouveau_drm *drm = chan->drm;
> > -	struct drm_nouveau_gem_pushbuf_bo __user *upbbo =
> > -				(void __force __user *)(uintptr_t)user_pbbo_ptr;
> >  	struct nouveau_bo *nvbo;
> >  	int ret, relocs = 0;
> >  
> > @@ -531,10 +528,6 @@ validate_list(struct nouveau_channel *chan, struct nouveau_cli *cli,
> >  			b->presumed.offset = nvbo->bo.offset;
> >  			b->presumed.valid = 0;
> >  			relocs++;
> > -
> > -			if (copy_to_user(&upbbo[nvbo->pbbo_index].presumed,
> > -					     &b->presumed, sizeof(b->presumed)))
> > -				return -EFAULT;
> >  		}
> >  	}
> >  
> > @@ -545,8 +538,8 @@ static int
> >  nouveau_gem_pushbuf_validate(struct nouveau_channel *chan,
> >  			     struct drm_file *file_priv,
> >  			     struct drm_nouveau_gem_pushbuf_bo *pbbo,
> > -			     uint64_t user_buffers, int nr_buffers,
> > -			     struct validate_op *op, int *apply_relocs)
> > +			     int nr_buffers,
> > +			     struct validate_op *op, bool *apply_relocs)
> >  {
> >  	struct nouveau_cli *cli = nouveau_cli(file_priv);
> >  	int ret;
> > @@ -563,7 +556,7 @@ nouveau_gem_pushbuf_validate(struct nouveau_channel *chan,
> >  		return ret;
> >  	}
> >  
> > -	ret = validate_list(chan, cli, &op->list, pbbo, user_buffers);
> > +	ret = validate_list(chan, cli, &op->list, pbbo);
> >  	if (unlikely(ret < 0)) {
> >  		if (ret != -ERESTARTSYS)
> >  			NV_PRINTK(err, cli, "validating bo list\n");
> > @@ -603,16 +596,12 @@ u_memcpya(uint64_t user, unsigned nmemb, unsigned size)
> >  static int
> >  nouveau_gem_pushbuf_reloc_apply(struct nouveau_cli *cli,
> >  				struct drm_nouveau_gem_pushbuf *req,
> > +				struct drm_nouveau_gem_pushbuf_reloc *reloc,
> >  				struct drm_nouveau_gem_pushbuf_bo *bo)
> >  {
> > -	struct drm_nouveau_gem_pushbuf_reloc *reloc = NULL;
> >  	int ret = 0;
> >  	unsigned i;
> >  
> > -	reloc = u_memcpya(req->relocs, req->nr_relocs, sizeof(*reloc));
> > -	if (IS_ERR(reloc))
> > -		return PTR_ERR(reloc);
> > -
> >  	for (i = 0; i < req->nr_relocs; i++) {
> >  		struct drm_nouveau_gem_pushbuf_reloc *r = &reloc[i];
> >  		struct drm_nouveau_gem_pushbuf_bo *b;
> > @@ -691,11 +680,13 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void *data,
> >  	struct nouveau_drm *drm = nouveau_drm(dev);
> >  	struct drm_nouveau_gem_pushbuf *req = data;
> >  	struct drm_nouveau_gem_pushbuf_push *push;
> > +	struct drm_nouveau_gem_pushbuf_reloc *reloc = NULL;
> >  	struct drm_nouveau_gem_pushbuf_bo *bo;
> >  	struct nouveau_channel *chan = NULL;
> >  	struct validate_op op;
> >  	struct nouveau_fence *fence = NULL;
> > -	int i, j, ret = 0, do_reloc = 0;
> > +	int i, j, ret = 0;
> > +	bool do_reloc = false;
> >  
> >  	if (unlikely(!abi16))
> >  		return -ENOMEM;
> > @@ -753,7 +744,8 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void *data,
> >  	}
> >  
> >  	/* Validate buffer list */
> > -	ret = nouveau_gem_pushbuf_validate(chan, file_priv, bo, req->buffers,
> > +revalidate:
> > +	ret = nouveau_gem_pushbuf_validate(chan, file_priv, bo,
> >  					   req->nr_buffers, &op, &do_reloc);
> >  	if (ret) {
> >  		if (ret != -ERESTARTSYS)
> > @@ -763,7 +755,18 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void *data,
> >  
> >  	/* Apply any relocations that are required */
> >  	if (do_reloc) {
> > -		ret = nouveau_gem_pushbuf_reloc_apply(cli, req, bo);
> > +		if (!reloc) {
> > +			validate_fini(&op, chan, NULL, bo);
> > +			reloc = u_memcpya(req->relocs, req->nr_relocs, sizeof(*reloc));
> > +			if (IS_ERR(reloc)) {
> > +				ret = PTR_ERR(reloc);
> > +				goto out_prevalid;
> > +			}
> > +
> > +			goto revalidate;
> > +		}
> > +
> > +		ret = nouveau_gem_pushbuf_reloc_apply(cli, req, reloc, bo);
> >  		if (ret) {
> >  			NV_PRINTK(err, cli, "reloc apply: %d\n", ret);
> >  			goto out;
> > @@ -849,6 +852,22 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void *data,
> >  	validate_fini(&op, chan, fence, bo);
> >  	nouveau_fence_unref(&fence);
> >  
> > +	if (do_reloc) {
> > +		struct drm_nouveau_gem_pushbuf_bo __user *upbbo =
> > +			u64_to_user_ptr(req->buffers);
> > +
> > +		for (i = 0; i < req->nr_buffers; i++) {
> > +			if (bo[i].presumed.valid)
> > +				continue;
> > +
> > +			if (copy_to_user(&upbbo[i].presumed, &bo[i].presumed,
> > +					 sizeof(bo[i].presumed))) {
> > +				ret = -EFAULT;
> > +				break;
> > +			}
> > +		}
> > +		u_free(reloc);
> > +	}
> >  out_prevalid:
> >  	u_free(bo);
> >  	u_free(push);
> > -- 
> > 2.23.0.rc1
> > 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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