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    Subject[PATCH v6 16/19] arm,arm64: do not always merge biovec if we are running on Xen
    Date
    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@eu.citrix.com>
    ---
    arch/arm/include/asm/io.h | 8 ++++++++
    arch/arm64/include/asm/io.h | 9 +++++++++
    drivers/xen/biomerge.c | 4 +++-
    3 files changed, 20 insertions(+), 1 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 */
    diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c
    index 0edb91c..f323a2d 100644
    --- a/drivers/xen/biomerge.c
    +++ b/drivers/xen/biomerge.c
    @@ -2,6 +2,7 @@
    #include <linux/io.h>
    #include <linux/export.h>
    #include <xen/page.h>
    +#include <xen/features.h>

    bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
    const struct bio_vec *vec2)
    @@ -9,7 +10,8 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
    unsigned long mfn1 = pfn_to_mfn(page_to_pfn(vec1->bv_page));
    unsigned long mfn2 = pfn_to_mfn(page_to_pfn(vec2->bv_page));

    - return __BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&
    + return !xen_feature(XENFEAT_auto_translated_physmap) &&
    + __BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&
    ((mfn1 == mfn2) || ((mfn1+1) == mfn2));
    }
    EXPORT_SYMBOL(xen_biovec_phys_mergeable);
    --
    1.7.2.5


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