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From: Roland Scheidegger <sroland@vmware.com>
To: Thomas Gleixner <tglx@linutronix.de>,
	LKML <linux-kernel@vger.kernel.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>,
	David Airlie <airlied@linux.ie>,
	nouveau@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	dri-devel@lists.freedesktop.org,
	virtualization@lists.linux-foundation.org, linux-mm@kvack.org,
	Huang Rui <ray.huang@amd.com>,
	VMware Graphics <linux-graphics-maintainer@vmware.com>,
	Gerd Hoffmann <kraxel@redhat.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	spice-devel@lists.freedesktop.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	Christian Koenig <christian.koenig@amd.com>,
	Zack Rusin <zackr@vmware.com>, Ben Skeggs <bskeggs@redhat.com>
Subject: Re: [Nouveau] [patch 2/7] drm/vmgfx: Replace kmap_atomic()
Date: Fri, 5 Mar 2021 16:35:42 +0100
Message-ID: <5ea9de05-31a1-855f-ab28-49c0cb6b724c@vmware.com> (raw)
In-Reply-To: <20210303132711.487711828@linutronix.de>

On 03.03.21 14:20, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> There is no reason to disable pagefaults and preemption as a side effect of
> kmap_atomic_prot().
> 
> Use kmap_local_page_prot() instead and document the reasoning for the
> mapping usage with the given pgprot.
> 
> Remove the NULL pointer check for the map. These functions return a valid
> address for valid pages and the return was bogus anyway as it would have
> left preemption and pagefaults disabled.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
> Cc: Roland Scheidegger <sroland@vmware.com>
> Cc: Zack Rusin <zackr@vmware.com>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: dri-devel@lists.freedesktop.org
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_blit.c |   30 ++++++++++++------------------
>  1 file changed, 12 insertions(+), 18 deletions(-)
> 
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_blit.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_blit.c
> @@ -375,12 +375,12 @@ static int vmw_bo_cpu_blit_line(struct v
>  		copy_size = min_t(u32, copy_size, PAGE_SIZE - src_page_offset);
>  
>  		if (unmap_src) {
> -			kunmap_atomic(d->src_addr);
> +			kunmap_local(d->src_addr);
>  			d->src_addr = NULL;
>  		}
>  
>  		if (unmap_dst) {
> -			kunmap_atomic(d->dst_addr);
> +			kunmap_local(d->dst_addr);
>  			d->dst_addr = NULL;
>  		}
>  
> @@ -388,12 +388,8 @@ static int vmw_bo_cpu_blit_line(struct v
>  			if (WARN_ON_ONCE(dst_page >= d->dst_num_pages))
>  				return -EINVAL;
>  
> -			d->dst_addr =
> -				kmap_atomic_prot(d->dst_pages[dst_page],
> -						 d->dst_prot);
> -			if (!d->dst_addr)
> -				return -ENOMEM;
> -
> +			d->dst_addr = kmap_local_page_prot(d->dst_pages[dst_page],
> +							   d->dst_prot);
>  			d->mapped_dst = dst_page;
>  		}
>  
> @@ -401,12 +397,8 @@ static int vmw_bo_cpu_blit_line(struct v
>  			if (WARN_ON_ONCE(src_page >= d->src_num_pages))
>  				return -EINVAL;
>  
> -			d->src_addr =
> -				kmap_atomic_prot(d->src_pages[src_page],
> -						 d->src_prot);
> -			if (!d->src_addr)
> -				return -ENOMEM;
> -
> +			d->src_addr = kmap_local_page_prot(d->src_pages[src_page],
> +							   d->src_prot);
>  			d->mapped_src = src_page;
>  		}
>  		diff->do_cpy(diff, d->dst_addr + dst_page_offset,
> @@ -436,8 +428,10 @@ static int vmw_bo_cpu_blit_line(struct v
>   *
>   * Performs a CPU blit from one buffer object to another avoiding a full
>   * bo vmap which may exhaust- or fragment vmalloc space.
> - * On supported architectures (x86), we're using kmap_atomic which avoids
> - * cross-processor TLB- and cache flushes and may, on non-HIGHMEM systems
> + *
> + * On supported architectures (x86), we're using kmap_local_prot() which
> + * avoids cross-processor TLB- and cache flushes. kmap_local_prot() will
> + * either map a highmem page with the proper pgprot on HIGHMEM=y systems or
>   * reference already set-up mappings.
>   *
>   * Neither of the buffer objects may be placed in PCI memory
> @@ -500,9 +494,9 @@ int vmw_bo_cpu_blit(struct ttm_buffer_ob
>  	}
>  out:
>  	if (d.src_addr)
> -		kunmap_atomic(d.src_addr);
> +		kunmap_local(d.src_addr);
>  	if (d.dst_addr)
> -		kunmap_atomic(d.dst_addr);
> +		kunmap_local(d.dst_addr);
>  
>  	return ret;
>  }
> 
> 

Seems reasonable to me.
Reviewed-by: Roland Scheidegger <sroland@vmware.com>

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  parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-03 13:20 [Nouveau] [patch 0/7] drm, highmem: Cleanup io/kmap_atomic*() usage Thomas Gleixner
2021-03-03 13:20 ` [Nouveau] [patch 1/7] drm/ttm: Replace kmap_atomic() usage Thomas Gleixner
2021-03-04 17:42   ` Christian König
2021-03-03 13:20 ` [Nouveau] [patch 2/7] drm/vmgfx: Replace kmap_atomic() Thomas Gleixner
2021-03-04 18:47   ` Zack Rusin
2021-03-05 15:35   ` Roland Scheidegger [this message]
2021-03-03 13:20 ` [Nouveau] [patch 3/7] highmem: Remove kmap_atomic_prot() Thomas Gleixner
2021-03-03 13:20 ` [Nouveau] [patch 4/7] drm/qxl: Replace io_mapping_map_atomic_wc() Thomas Gleixner
2021-03-03 13:20 ` [Nouveau] [patch 5/7] drm/nouveau/device: " Thomas Gleixner
2021-03-03 13:20 ` [Nouveau] [patch 6/7] drm/i915: " Thomas Gleixner
2021-03-03 13:20 ` [Nouveau] [patch 7/7] io-mapping: Remove io_mapping_map_atomic_wc() Thomas Gleixner

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