xen/arm/arm64: introduce xen_arch_need_swiotlb

commit a4dba130891271084344c12537731542ec77cb85 upstream.

Introduce an arch specific function to find out whether a particular dma
mapping operation needs to bounce on the swiotlb buffer.

On ARM and ARM64, if the page involved is a foreign page and the device
is not coherent, we need to bounce because at unmap time we cannot
execute any required cache maintenance operations (we don't know how to
find the pfn from the mfn).

No change of behaviour for x86.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[ stefano: The commit needs to be slightly modified because
  is_device_dma_coherent is not available on kernels < 3.19, so I just
  removed the call, thus assuming that the device is not coherent on arm
  (slower but safe) ]
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
[ luis: backported to 3.16: used backport by stefano ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/arch/arm/include/asm/xen/page.h b/arch/arm/include/asm/xen/page.h
index ded062f9b358038c05fa074816706c40619e6408..df89aa3b1f03629e94deebccf4d45c893d6999d8 100644 (file)
--- a/arch/arm/include/asm/xen/page.h
+++ b/arch/arm/include/asm/xen/page.h
@@ -116,4 +116,8 @@ static inline bool set_phys_to_machine(unsigned long pfn, unsigned long mfn)
 #define xen_remap(cookie, size) ioremap_cache((cookie), (size))
 #define xen_unmap(cookie) iounmap((cookie))
 
+bool xen_arch_need_swiotlb(struct device *dev,
+                          unsigned long pfn,
+                          unsigned long mfn);
+
 #endif /* _ASM_ARM_XEN_PAGE_H */

diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index b0e77de9914866e19fb69ab28f9cd674d7e7f57d..f8a576b1d9bb00071158178408807dee021b4cff 100644 (file)
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -16,6 +16,13 @@
 #include <asm/xen/hypercall.h>
 #include <asm/xen/interface.h>
 
+bool xen_arch_need_swiotlb(struct device *dev,
+                          unsigned long pfn,
+                          unsigned long mfn)
+{
+       return (pfn != mfn);
+}
+
 int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
                                 unsigned int address_bits,
                                 dma_addr_t *dma_handle)

diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index c949923a56685463465b9281b3b4d5cb1c28a7d6..f58ef6c0613b6739351e4366a3b869c9c2ecb72b 100644 (file)
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -236,4 +236,11 @@ void make_lowmem_page_readwrite(void *vaddr);
 #define xen_remap(cookie, size) ioremap((cookie), (size));
 #define xen_unmap(cookie) iounmap((cookie))
 
+static inline bool xen_arch_need_swiotlb(struct device *dev,
+                                        unsigned long pfn,
+                                        unsigned long mfn)
+{
+       return false;
+}
+
 #endif /* _ASM_X86_XEN_PAGE_H */

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 9df5d6ec7eecca0e7acb4cb955c3bf6dd7d5ad19..de37cc22b9a51c68aa099a7b49763a5d25244430 100644 (file)
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -397,7 +397,9 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
         * buffering it.
         */
        if (dma_capable(dev, dev_addr, size) &&
-           !range_straddles_page_boundary(phys, size) && !swiotlb_force) {
+           !range_straddles_page_boundary(phys, size) &&
+               !xen_arch_need_swiotlb(dev, PFN_DOWN(phys), PFN_DOWN(dev_addr)) &&
+               !swiotlb_force) {
                /* we are not interested in the dma_addr returned by
                 * xen_dma_map_page, only in the potential cache flushes executed
                 * by the function. */
@@ -555,6 +557,7 @@ xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
                dma_addr_t dev_addr = xen_phys_to_bus(paddr);
 
                if (swiotlb_force ||
+                   xen_arch_need_swiotlb(hwdev, PFN_DOWN(paddr), PFN_DOWN(dev_addr)) ||
                    !dma_capable(hwdev, dev_addr, sg->length) ||
                    range_straddles_page_boundary(paddr, sg->length)) {
                        phys_addr_t map = swiotlb_tbl_map_single(hwdev,