xen/swiotlb: Add support for 64KB page granularity

Swiotlb is used on ARM64 to support DMA on platform where devices are
not protected by an SMMU. Furthermore it's only enabled for DOM0.

While Xen is always using 4KB page granularity in the stage-2 page table,
Linux ARM64 may either use 4KB or 64KB. This means that a Linux page
can be spanned accross multiple Xen page.

The Swiotlb code has to validate that the buffer used for DMA is
physically contiguous in the memory. As a Linux page can't be shared
between local memory and foreign page by design (the balloon code always
removing entirely a Linux page), the changes in the code are very
minimal because we only need to check the first Xen PFN.

Note that it may be possible to optimize the function
check_page_physically_contiguous to avoid looping over every Xen PFN
for local memory. Although I will let this optimization for a follow-up.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 19 insertions, 20 deletions

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 0a5a0e9..7399782 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -76,27 +76,27 @@ static unsigned long xen_io_tlb_nslabs;
 static u64 start_dma_addr;
 
 /*
- * Both of these functions should avoid PFN_PHYS because phys_addr_t
+ * Both of these functions should avoid XEN_PFN_PHYS because phys_addr_t
  * can be 32bit when dma_addr_t is 64bit leading to a loss in
  * information if the shift is done before casting to 64bit.
  */
 static inline dma_addr_t xen_phys_to_bus(phys_addr_t paddr)
 {
-	unsigned long bfn = pfn_to_bfn(PFN_DOWN(paddr));
-	dma_addr_t dma = (dma_addr_t)bfn << PAGE_SHIFT;
+	unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr));
+	dma_addr_t dma = (dma_addr_t)bfn << XEN_PAGE_SHIFT;
 
-	dma |= paddr & ~PAGE_MASK;
+	dma |= paddr & ~XEN_PAGE_MASK;
 
 	return dma;
 }
 
 static inline phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
 {
-	unsigned long pfn = bfn_to_pfn(PFN_DOWN(baddr));
-	dma_addr_t dma = (dma_addr_t)pfn << PAGE_SHIFT;
+	unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr));
+	dma_addr_t dma = (dma_addr_t)xen_pfn << XEN_PAGE_SHIFT;
 	phys_addr_t paddr = dma;
 
-	paddr |= baddr & ~PAGE_MASK;
+	paddr |= baddr & ~XEN_PAGE_MASK;
 
 	return paddr;
 }
@@ -106,7 +106,7 @@ static inline dma_addr_t xen_virt_to_bus(void *address)
 	return xen_phys_to_bus(virt_to_phys(address));
 }
 
-static int check_pages_physically_contiguous(unsigned long pfn,
+static int check_pages_physically_contiguous(unsigned long xen_pfn,
 					     unsigned int offset,
 					     size_t length)
 {
@@ -114,11 +114,11 @@ static int check_pages_physically_contiguous(unsigned long pfn,
 	int i;
 	int nr_pages;
 
-	next_bfn = pfn_to_bfn(pfn);
-	nr_pages = (offset + length + PAGE_SIZE-1) >> PAGE_SHIFT;
+	next_bfn = pfn_to_bfn(xen_pfn);
+	nr_pages = (offset + length + XEN_PAGE_SIZE-1) >> XEN_PAGE_SHIFT;
 
 	for (i = 1; i < nr_pages; i++) {
-		if (pfn_to_bfn(++pfn) != ++next_bfn)
+		if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
 			return 0;
 	}
 	return 1;
@@ -126,28 +126,27 @@ static int check_pages_physically_contiguous(unsigned long pfn,
 
 static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
 {
-	unsigned long pfn = PFN_DOWN(p);
-	unsigned int offset = p & ~PAGE_MASK;
+	unsigned long xen_pfn = XEN_PFN_DOWN(p);
+	unsigned int offset = p & ~XEN_PAGE_MASK;
 
-	if (offset + size <= PAGE_SIZE)
+	if (offset + size <= XEN_PAGE_SIZE)
 		return 0;
-	if (check_pages_physically_contiguous(pfn, offset, size))
+	if (check_pages_physically_contiguous(xen_pfn, offset, size))
 		return 0;
 	return 1;
 }
 
 static int is_xen_swiotlb_buffer(dma_addr_t dma_addr)
 {
-	unsigned long bfn = PFN_DOWN(dma_addr);
-	unsigned long pfn = bfn_to_local_pfn(bfn);
-	phys_addr_t paddr;
+	unsigned long bfn = XEN_PFN_DOWN(dma_addr);
+	unsigned long xen_pfn = bfn_to_local_pfn(bfn);
+	phys_addr_t paddr = XEN_PFN_PHYS(xen_pfn);
 
 	/* If the address is outside our domain, it CAN
 	 * have the same virtual address as another address
 	 * in our domain. Therefore _only_ check address within our domain.
 	 */
-	if (pfn_valid(pfn)) {
-		paddr = PFN_PHYS(pfn);
+	if (pfn_valid(PFN_DOWN(paddr))) {
 		return paddr >= virt_to_phys(xen_io_tlb_start) &&
 		       paddr < virt_to_phys(xen_io_tlb_end);
 	}