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* [PATCH v2] xen/arm: correctly handle DMA mapping of compound pages
@ 2016-02-08 16:02 Ian Campbell
  0 siblings, 0 replies; 4+ messages in thread
From: Ian Campbell @ 2016-02-08 16:02 UTC (permalink / raw)
  To: Stefano Stabellini
  Cc: Russell King, Ian Campbell, Catalin Marinas, Will Deacon,
	xen-devel, linux-arm-kernel

Currently xen_dma_map_page concludes that DMA to anything other than
the head page of a compound page must be foreign, since the PFN of the
page is that of the head.

Fix the check to instead consider the whole of a compound page to be
local if the PFN of the head passes the 1:1 check.

We can never see a compound page which is a mixture of foreign and
local sub-pages.

The comment already correctly described the intention, but fixup the
spelling and some grammar.

This fixes the various SSH protocol errors which we have been seeing
on the cubietrucks in our automated test infrastructure.

This has been broken since commit 3567258d281b ("xen/arm: use
hypercall to flush caches in map_page"), which was in v3.19-rc1.

NB arch/arm64/.../xen/page-coherent.h also includes this file.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: xen-devel@lists.xenproject.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: stable@vger.kernel.org # v3.19+
---
v2: Placate checkpatch
    Handle 64K pages
    Add some ()s
---
 arch/arm/include/asm/xen/page-coherent.h | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/arm/include/asm/xen/page-coherent.h b/arch/arm/include/asm/xen/page-coherent.h
index 0375c8c..9408a99 100644
--- a/arch/arm/include/asm/xen/page-coherent.h
+++ b/arch/arm/include/asm/xen/page-coherent.h
@@ -35,14 +35,21 @@ static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
 	     dma_addr_t dev_addr, unsigned long offset, size_t size,
 	     enum dma_data_direction dir, struct dma_attrs *attrs)
 {
-	bool local = XEN_PFN_DOWN(dev_addr) == page_to_xen_pfn(page);
+	unsigned long page_pfn = page_to_xen_pfn(page);
+	unsigned long dev_pfn = XEN_PFN_DOWN(dev_addr);
+	unsigned long compound_pages =
+		(1<<compound_order(page)) * XEN_PFN_PER_PAGE;
+	bool local = (page_pfn <= dev_pfn) &&
+		(dev_pfn - page_pfn < compound_pages);
+
 	/*
-	 * Dom0 is mapped 1:1, while the Linux page can be spanned accross
-	 * multiple Xen page, it's not possible to have a mix of local and
-	 * foreign Xen page. So if the first xen_pfn == mfn the page is local
-	 * otherwise it's a foreign page grant-mapped in dom0. If the page is
-	 * local we can safely call the native dma_ops function, otherwise we
-	 * call the xen specific function.
+	 * Dom0 is mapped 1:1, while the Linux page can span across
+	 * multiple Xen pages, it's not possible for it to contain a
+	 * mix of local and foreign Xen pages. So if the first xen_pfn
+	 * == mfn the page is local otherwise it's a foreign page
+	 * grant-mapped in dom0. If the page is local we can safely
+	 * call the native dma_ops function, otherwise we call the xen
+	 * specific function.
 	 */
 	if (local)
 		__generic_dma_ops(hwdev)->map_page(hwdev, page, offset, size, dir, attrs);
-- 
2.1.4

^ permalink raw reply related	[flat|nested] 4+ messages in thread
* [PATCH v2] xen/arm: correctly handle DMA mapping of compound pages
  2016-02-08 16:02 Ian Campbell
@ 2016-02-08 16:59   ` Stefano Stabellini
  0 siblings, 0 replies; 4+ messages in thread
From: Stefano Stabellini @ 2016-02-08 16:59 UTC (permalink / raw)
  To: linux-arm-kernel

On Mon, 8 Feb 2016, Ian Campbell wrote:
> Currently xen_dma_map_page concludes that DMA to anything other than
> the head page of a compound page must be foreign, since the PFN of the
> page is that of the head.
> 
> Fix the check to instead consider the whole of a compound page to be
> local if the PFN of the head passes the 1:1 check.
> 
> We can never see a compound page which is a mixture of foreign and
> local sub-pages.
> 
> The comment already correctly described the intention, but fixup the
> spelling and some grammar.
> 
> This fixes the various SSH protocol errors which we have been seeing
> on the cubietrucks in our automated test infrastructure.
> 
> This has been broken since commit 3567258d281b ("xen/arm: use
> hypercall to flush caches in map_page"), which was in v3.19-rc1.
> 
> NB arch/arm64/.../xen/page-coherent.h also includes this file.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: xen-devel at lists.xenproject.org
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: stable at vger.kernel.org # v3.19+

Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

I'll add it to my queue.


> v2: Placate checkpatch
>     Handle 64K pages
>     Add some ()s
> ---
>  arch/arm/include/asm/xen/page-coherent.h | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm/include/asm/xen/page-coherent.h b/arch/arm/include/asm/xen/page-coherent.h
> index 0375c8c..9408a99 100644
> --- a/arch/arm/include/asm/xen/page-coherent.h
> +++ b/arch/arm/include/asm/xen/page-coherent.h
> @@ -35,14 +35,21 @@ static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
>  	     dma_addr_t dev_addr, unsigned long offset, size_t size,
>  	     enum dma_data_direction dir, struct dma_attrs *attrs)
>  {
> -	bool local = XEN_PFN_DOWN(dev_addr) == page_to_xen_pfn(page);
> +	unsigned long page_pfn = page_to_xen_pfn(page);
> +	unsigned long dev_pfn = XEN_PFN_DOWN(dev_addr);
> +	unsigned long compound_pages =
> +		(1<<compound_order(page)) * XEN_PFN_PER_PAGE;
> +	bool local = (page_pfn <= dev_pfn) &&
> +		(dev_pfn - page_pfn < compound_pages);
> +
>  	/*
> -	 * Dom0 is mapped 1:1, while the Linux page can be spanned accross
> -	 * multiple Xen page, it's not possible to have a mix of local and
> -	 * foreign Xen page. So if the first xen_pfn == mfn the page is local
> -	 * otherwise it's a foreign page grant-mapped in dom0. If the page is
> -	 * local we can safely call the native dma_ops function, otherwise we
> -	 * call the xen specific function.
> +	 * Dom0 is mapped 1:1, while the Linux page can span across
> +	 * multiple Xen pages, it's not possible for it to contain a
> +	 * mix of local and foreign Xen pages. So if the first xen_pfn
> +	 * == mfn the page is local otherwise it's a foreign page
> +	 * grant-mapped in dom0. If the page is local we can safely
> +	 * call the native dma_ops function, otherwise we call the xen
> +	 * specific function.
>  	 */
>  	if (local)
>  		__generic_dma_ops(hwdev)->map_page(hwdev, page, offset, size, dir, attrs);
> -- 
> 2.1.4
> 

^ permalink raw reply	[flat|nested] 4+ messages in thread
* Re: [PATCH v2] xen/arm: correctly handle DMA mapping of compound pages
@ 2016-02-08 16:59   ` Stefano Stabellini
  0 siblings, 0 replies; 4+ messages in thread
From: Stefano Stabellini @ 2016-02-08 16:59 UTC (permalink / raw)
  To: Ian Campbell
  Cc: Russell King, Stefano Stabellini, Catalin Marinas, Will Deacon,
	xen-devel, linux-arm-kernel

On Mon, 8 Feb 2016, Ian Campbell wrote:
> Currently xen_dma_map_page concludes that DMA to anything other than
> the head page of a compound page must be foreign, since the PFN of the
> page is that of the head.
> 
> Fix the check to instead consider the whole of a compound page to be
> local if the PFN of the head passes the 1:1 check.
> 
> We can never see a compound page which is a mixture of foreign and
> local sub-pages.
> 
> The comment already correctly described the intention, but fixup the
> spelling and some grammar.
> 
> This fixes the various SSH protocol errors which we have been seeing
> on the cubietrucks in our automated test infrastructure.
> 
> This has been broken since commit 3567258d281b ("xen/arm: use
> hypercall to flush caches in map_page"), which was in v3.19-rc1.
> 
> NB arch/arm64/.../xen/page-coherent.h also includes this file.
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: xen-devel@lists.xenproject.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: stable@vger.kernel.org # v3.19+

Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

I'll add it to my queue.


> v2: Placate checkpatch
>     Handle 64K pages
>     Add some ()s
> ---
>  arch/arm/include/asm/xen/page-coherent.h | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm/include/asm/xen/page-coherent.h b/arch/arm/include/asm/xen/page-coherent.h
> index 0375c8c..9408a99 100644
> --- a/arch/arm/include/asm/xen/page-coherent.h
> +++ b/arch/arm/include/asm/xen/page-coherent.h
> @@ -35,14 +35,21 @@ static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
>  	     dma_addr_t dev_addr, unsigned long offset, size_t size,
>  	     enum dma_data_direction dir, struct dma_attrs *attrs)
>  {
> -	bool local = XEN_PFN_DOWN(dev_addr) == page_to_xen_pfn(page);
> +	unsigned long page_pfn = page_to_xen_pfn(page);
> +	unsigned long dev_pfn = XEN_PFN_DOWN(dev_addr);
> +	unsigned long compound_pages =
> +		(1<<compound_order(page)) * XEN_PFN_PER_PAGE;
> +	bool local = (page_pfn <= dev_pfn) &&
> +		(dev_pfn - page_pfn < compound_pages);
> +
>  	/*
> -	 * Dom0 is mapped 1:1, while the Linux page can be spanned accross
> -	 * multiple Xen page, it's not possible to have a mix of local and
> -	 * foreign Xen page. So if the first xen_pfn == mfn the page is local
> -	 * otherwise it's a foreign page grant-mapped in dom0. If the page is
> -	 * local we can safely call the native dma_ops function, otherwise we
> -	 * call the xen specific function.
> +	 * Dom0 is mapped 1:1, while the Linux page can span across
> +	 * multiple Xen pages, it's not possible for it to contain a
> +	 * mix of local and foreign Xen pages. So if the first xen_pfn
> +	 * == mfn the page is local otherwise it's a foreign page
> +	 * grant-mapped in dom0. If the page is local we can safely
> +	 * call the native dma_ops function, otherwise we call the xen
> +	 * specific function.
>  	 */
>  	if (local)
>  		__generic_dma_ops(hwdev)->map_page(hwdev, page, offset, size, dir, attrs);
> -- 
> 2.1.4
> 

^ permalink raw reply	[flat|nested] 4+ messages in thread
* [PATCH v2] xen/arm: correctly handle DMA mapping of compound pages
@ 2016-02-08 16:02 Ian Campbell
  2016-02-08 16:59   ` Stefano Stabellini
  0 siblings, 1 reply; 4+ messages in thread
From: Ian Campbell @ 2016-02-08 16:02 UTC (permalink / raw)
  To: linux-arm-kernel

Currently xen_dma_map_page concludes that DMA to anything other than
the head page of a compound page must be foreign, since the PFN of the
page is that of the head.

Fix the check to instead consider the whole of a compound page to be
local if the PFN of the head passes the 1:1 check.

We can never see a compound page which is a mixture of foreign and
local sub-pages.

The comment already correctly described the intention, but fixup the
spelling and some grammar.

This fixes the various SSH protocol errors which we have been seeing
on the cubietrucks in our automated test infrastructure.

This has been broken since commit 3567258d281b ("xen/arm: use
hypercall to flush caches in map_page"), which was in v3.19-rc1.

NB arch/arm64/.../xen/page-coherent.h also includes this file.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: xen-devel at lists.xenproject.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: stable at vger.kernel.org # v3.19+
---
v2: Placate checkpatch
    Handle 64K pages
    Add some ()s
---
 arch/arm/include/asm/xen/page-coherent.h | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/arch/arm/include/asm/xen/page-coherent.h b/arch/arm/include/asm/xen/page-coherent.h
index 0375c8c..9408a99 100644
--- a/arch/arm/include/asm/xen/page-coherent.h
+++ b/arch/arm/include/asm/xen/page-coherent.h
@@ -35,14 +35,21 @@ static inline void xen_dma_map_page(struct device *hwdev, struct page *page,
 	     dma_addr_t dev_addr, unsigned long offset, size_t size,
 	     enum dma_data_direction dir, struct dma_attrs *attrs)
 {
-	bool local = XEN_PFN_DOWN(dev_addr) == page_to_xen_pfn(page);
+	unsigned long page_pfn = page_to_xen_pfn(page);
+	unsigned long dev_pfn = XEN_PFN_DOWN(dev_addr);
+	unsigned long compound_pages =
+		(1<<compound_order(page)) * XEN_PFN_PER_PAGE;
+	bool local = (page_pfn <= dev_pfn) &&
+		(dev_pfn - page_pfn < compound_pages);
+
 	/*
-	 * Dom0 is mapped 1:1, while the Linux page can be spanned accross
-	 * multiple Xen page, it's not possible to have a mix of local and
-	 * foreign Xen page. So if the first xen_pfn == mfn the page is local
-	 * otherwise it's a foreign page grant-mapped in dom0. If the page is
-	 * local we can safely call the native dma_ops function, otherwise we
-	 * call the xen specific function.
+	 * Dom0 is mapped 1:1, while the Linux page can span across
+	 * multiple Xen pages, it's not possible for it to contain a
+	 * mix of local and foreign Xen pages. So if the first xen_pfn
+	 * == mfn the page is local otherwise it's a foreign page
+	 * grant-mapped in dom0. If the page is local we can safely
+	 * call the native dma_ops function, otherwise we call the xen
+	 * specific function.
 	 */
 	if (local)
 		__generic_dma_ops(hwdev)->map_page(hwdev, page, offset, size, dir, attrs);
-- 
2.1.4

^ permalink raw reply related	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2016-02-08 16:59 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2016-02-08 16:02 [PATCH v2] xen/arm: correctly handle DMA mapping of compound pages Ian Campbell
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2016-02-08 16:02 Ian Campbell
2016-02-08 16:59 ` Stefano Stabellini
2016-02-08 16:59   ` Stefano Stabellini

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