linux-kernel - Re: [PATCH v8 16/19] arm,arm64: do not always merge biovec if we are running on Xen

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Date:	Fri, 18 Oct 2013 13:23:59 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	<xen-devel@...ts.xensource.com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <konrad.wilk@...cle.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	Catalin Marinas <catalin.marinas@....com>,
	<linux@....linux.org.uk>
Subject: Re: [PATCH v8 16/19] arm,arm64: do not always merge biovec if we
 are running on Xen

Russell, Catalin,
are you OK with this patch?

It shouldn't have any impact when running on native, only on Xen.


On Thu, 17 Oct 2013, Stefano Stabellini wrote:
> This is similar to what it is done on X86: biovecs are prevented from merging
> otherwise every dma requests would be forced to bounce on the swiotlb buffer.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> 
> 
> Changes in v7:
> - remove the extra autotranslate check in biomerge.c.
> ---
>  arch/arm/include/asm/io.h   |    8 ++++++++
>  arch/arm64/include/asm/io.h |    9 +++++++++
>  2 files changed, 17 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/include/asm/io.h b/arch/arm/include/asm/io.h
> index d070741..c45effc 100644
> --- a/arch/arm/include/asm/io.h
> +++ b/arch/arm/include/asm/io.h
> @@ -24,9 +24,11 @@
>  #ifdef __KERNEL__
>  
>  #include <linux/types.h>
> +#include <linux/blk_types.h>
>  #include <asm/byteorder.h>
>  #include <asm/memory.h>
>  #include <asm-generic/pci_iomap.h>
> +#include <xen/xen.h>
>  
>  /*
>   * ISA I/O bus memory addresses are 1:1 with the physical address.
> @@ -372,6 +374,12 @@ extern void pci_iounmap(struct pci_dev *dev, void __iomem *addr);
>  #define BIOVEC_MERGEABLE(vec1, vec2)	\
>  	((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2)))
>  
> +extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
> +				      const struct bio_vec *vec2);
> +#define BIOVEC_PHYS_MERGEABLE(vec1, vec2)				\
> +	(__BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&				\
> +	 (!xen_domain() || xen_biovec_phys_mergeable(vec1, vec2)))
> +
>  #ifdef CONFIG_MMU
>  #define ARCH_HAS_VALID_PHYS_ADDR_RANGE
>  extern int valid_phys_addr_range(phys_addr_t addr, size_t size);
> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
> index 1d12f89..c163287b 100644
> --- a/arch/arm64/include/asm/io.h
> +++ b/arch/arm64/include/asm/io.h
> @@ -22,11 +22,14 @@
>  #ifdef __KERNEL__
>  
>  #include <linux/types.h>
> +#include <linux/blk_types.h>
>  
>  #include <asm/byteorder.h>
>  #include <asm/barrier.h>
>  #include <asm/pgtable.h>
>  
> +#include <xen/xen.h>
> +
>  /*
>   * Generic IO read/write.  These perform native-endian accesses.
>   */
> @@ -263,5 +266,11 @@ extern int devmem_is_allowed(unsigned long pfn);
>   */
>  #define xlate_dev_kmem_ptr(p)	p
>  
> +extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
> +				      const struct bio_vec *vec2);
> +#define BIOVEC_PHYS_MERGEABLE(vec1, vec2)				\
> +	(__BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&				\
> +	 (!xen_domain() || xen_biovec_phys_mergeable(vec1, vec2)))
> +
>  #endif	/* __KERNEL__ */
>  #endif	/* __ASM_IO_H */
> -- 
> 1.7.2.5
> 
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