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SubjectRe: [PATCH v2] xen: Add __GFP_DMA flag when xen_swiotlb_init gets free pages on ARM
On Fri, Apr 24, 2015 at 03:31:53PM +0100, Stefano Stabellini wrote:
> On Fri, 24 Apr 2015, Konrad Rzeszutek Wilk wrote:
> > On Fri, Apr 24, 2015 at 10:16:40AM +0100, Stefano Stabellini wrote:
> > > Make sure that xen_swiotlb_init allocates buffers that are DMA capable
> > > when at least one memblock is available below 4G. Otherwise we assume
> > > that all devices on the SoC can cope with >4G addresses. We do this on
> > > ARM and ARM64, where dom0 is mapped 1:1, so pfn == mfn in this case.
> > >
> > > No functional changes on x86.
> > >
> > > From: Chen Baozi <baozich@gmail.com>
> > >
> > > Signed-off-by: Chen Baozi <baozich@gmail.com>
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > > Tested-by: Chen Baozi <baozich@gmail.com>
> >
> > Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>
> Thanks! We are still early in the release cycle, should I add it to
> xentip/stable/for-linus-4.1?

Sure!
>
>
> > > diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
> > > index 2f7e6ff..0b579b2 100644
> > > --- a/arch/arm/include/asm/xen/page.h
> > > +++ b/arch/arm/include/asm/xen/page.h
> > > @@ -110,5 +110,6 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
> > > bool xen_arch_need_swiotlb(struct device *dev,
> > > unsigned long pfn,
> > > unsigned long mfn);
> > > +unsigned long xen_get_swiotlb_free_pages(unsigned int order);
> > >
> > > #endif /* _ASM_ARM_XEN_PAGE_H */
> > > diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
> > > index 793551d..4983250 100644
> > > --- a/arch/arm/xen/mm.c
> > > +++ b/arch/arm/xen/mm.c
> > > @@ -4,6 +4,7 @@
> > > #include <linux/gfp.h>
> > > #include <linux/highmem.h>
> > > #include <linux/export.h>
> > > +#include <linux/memblock.h>
> > > #include <linux/of_address.h>
> > > #include <linux/slab.h>
> > > #include <linux/types.h>
> > > @@ -21,6 +22,20 @@
> > > #include <asm/xen/hypercall.h>
> > > #include <asm/xen/interface.h>
> > >
> > > +unsigned long xen_get_swiotlb_free_pages(unsigned int order)
> > > +{
> > > + struct memblock_region *reg;
> > > + gfp_t flags = __GFP_NOWARN;
> > > +
> > > + for_each_memblock(memory, reg) {
> > > + if (reg->base < (phys_addr_t)0xffffffff) {
> > > + flags |= __GFP_DMA;
> > > + break;
> > > + }
> > > + }
> > > + return __get_free_pages(flags, order);
> > > +}
> > > +
> > > enum dma_cache_op {
> > > DMA_UNMAP,
> > > DMA_MAP,
> > > diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
> > > index 358dcd3..c44a5d5 100644
> > > --- a/arch/x86/include/asm/xen/page.h
> > > +++ b/arch/x86/include/asm/xen/page.h
> > > @@ -269,4 +269,9 @@ static inline bool xen_arch_need_swiotlb(struct device *dev,
> > > return false;
> > > }
> > >
> > > +static inline unsigned long xen_get_swiotlb_free_pages(unsigned int order)
> > > +{
> > > + return __get_free_pages(__GFP_NOWARN, order);
> > > +}
> > > +
> > > #endif /* _ASM_X86_XEN_PAGE_H */
> > > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> > > index 810ad41..4c54932 100644
> > > --- a/drivers/xen/swiotlb-xen.c
> > > +++ b/drivers/xen/swiotlb-xen.c
> > > @@ -235,7 +235,7 @@ retry:
> > > #define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
> > > #define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
> > > while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
> > > - xen_io_tlb_start = (void *)__get_free_pages(__GFP_NOWARN, order);
> > > + xen_io_tlb_start = (void *)xen_get_swiotlb_free_pages(order);
> > > if (xen_io_tlb_start)
> > > break;
> > > order--;
> >


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