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Message-Id: <50C0ADB502000078000AE9DA@nat28.tlf.novell.com> Date: Thu, 06 Dec 2012 13:37:41 +0000 From: "Jan Beulich" <JBeulich@...e.com> To: "Dongxiao Xu" <dongxiao.xu@...el.com> Cc: <xen-devel@...ts.xen.org>, <konrad.wilk@...cle.com>, <linux-kernel@...r.kernel.org> Subject: Re: [Xen-devel] [PATCH] xen/swiotlb: Exchange to contiguous memory for map_sg hook >>> On 06.12.12 at 14:08, Dongxiao Xu <dongxiao.xu@...el.com> wrote: > While mapping sg buffers, checking to cross page DMA buffer is > also needed. If the guest DMA buffer crosses page boundary, Xen > should exchange contiguous memory for it. > > Besides, it is needed to backup the original page contents > and copy it back after memory exchange is done. > > This fixes issues if device DMA into software static buffers, > and in case the static buffer cross page boundary which pages are > not contiguous in real hardware. > > Signed-off-by: Dongxiao Xu <dongxiao.xu@...el.com> > Signed-off-by: Xiantao Zhang <xiantao.zhang@...el.com> > --- > drivers/xen/swiotlb-xen.c | 47 > ++++++++++++++++++++++++++++++++++++++++++++- > 1 files changed, 46 insertions(+), 1 deletions(-) > > diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c > index 58db6df..e8f0cfb 100644 > --- a/drivers/xen/swiotlb-xen.c > +++ b/drivers/xen/swiotlb-xen.c > @@ -461,6 +461,22 @@ xen_swiotlb_sync_single_for_device(struct device *hwdev, > dma_addr_t dev_addr, > } > EXPORT_SYMBOL_GPL(xen_swiotlb_sync_single_for_device); > > +static bool > +check_continguous_region(unsigned long vstart, unsigned long order) check_continguous_region(unsigned long vstart, unsigned int order) But - why do you need to do this check order based in the first place? Checking the actual length of the buffer should suffice. > +{ > + unsigned long prev_ma = xen_virt_to_bus((void *)vstart); > + unsigned long next_ma; phys_addr_t or some such for both of them. > + int i; unsigned long > + > + for (i = 1; i < (1 << order); i++) { 1UL > + next_ma = xen_virt_to_bus((void *)(vstart + i * PAGE_SIZE)); > + if (next_ma != prev_ma + PAGE_SIZE) > + return false; > + prev_ma = next_ma; > + } > + return true; > +} > + > /* > * Map a set of buffers described by scatterlist in streaming mode for DMA. > * This is the scatter-gather version of the above xen_swiotlb_map_page > @@ -489,7 +505,36 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct > scatterlist *sgl, > > for_each_sg(sgl, sg, nelems, i) { > phys_addr_t paddr = sg_phys(sg); > - dma_addr_t dev_addr = xen_phys_to_bus(paddr); > + unsigned long vstart, order; > + dma_addr_t dev_addr; > + > + /* > + * While mapping sg buffers, checking to cross page DMA buffer > + * is also needed. If the guest DMA buffer crosses page > + * boundary, Xen should exchange contiguous memory for it. > + * Besides, it is needed to backup the original page contents > + * and copy it back after memory exchange is done. > + */ > + if (range_straddles_page_boundary(paddr, sg->length)) { > + vstart = (unsigned long)__va(paddr & PAGE_MASK); > + order = get_order(sg->length + (paddr & ~PAGE_MASK)); > + if (!check_continguous_region(vstart, order)) { > + unsigned long buf; > + buf = __get_free_pages(GFP_KERNEL, order); > + memcpy((void *)buf, (void *)vstart, > + PAGE_SIZE * (1 << order)); > + if (xen_create_contiguous_region(vstart, order, > + fls64(paddr))) { > + free_pages(buf, order); > + return 0; > + } > + memcpy((void *)vstart, (void *)buf, > + PAGE_SIZE * (1 << order)); > + free_pages(buf, order); > + } > + } > + > + dev_addr = xen_phys_to_bus(paddr); > > if (swiotlb_force || > !dma_capable(hwdev, dev_addr, sg->length) || How about swiotlb_map_page() (for the compound page case)? Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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