x86/dma: Remove dma_alloc_coherent_mask()

These days all devices (including the ISA fallback device) have a coherent
DMA mask set, so remove the workaround.

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Jon Mason <jdmason@kudzu.us>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Muli Ben-Yehuda <mulix@mulix.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: iommu@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/20180319103826.12853-3-hch@lst.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/dma-mapping.h

@@ -44,26 +44,12 @@ extern void dma_generic_free_coherent(struct device *dev, size_t size,
 				      void *vaddr, dma_addr_t dma_addr,
 				      unsigned long attrs);
 
-static inline unsigned long dma_alloc_coherent_mask(struct device *dev,
-						    gfp_t gfp)
-{
-	unsigned long dma_mask = 0;
-
-	dma_mask = dev->coherent_dma_mask;
-	if (!dma_mask)
-		dma_mask = (gfp & GFP_DMA) ? DMA_BIT_MASK(24) : DMA_BIT_MASK(32);
-
-	return dma_mask;
-}
-
 static inline gfp_t dma_alloc_coherent_gfp_flags(struct device *dev, gfp_t gfp)
 {
-	unsigned long dma_mask = dma_alloc_coherent_mask(dev, gfp);
-
-	if (dma_mask <= DMA_BIT_MASK(24))
+	if (dev->coherent_dma_mask <= DMA_BIT_MASK(24))
 		gfp |= GFP_DMA;
 #ifdef CONFIG_X86_64
-	if (dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
+	if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
 		gfp |= GFP_DMA32;
 #endif
        return gfp;

arch/x86/kernel/pci-dma.c

@@ -80,13 +80,10 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
 				 dma_addr_t *dma_addr, gfp_t flag,
 				 unsigned long attrs)
 {
-	unsigned long dma_mask;
 	struct page *page;
 	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	dma_addr_t addr;
 
-	dma_mask = dma_alloc_coherent_mask(dev, flag);
-
 again:
 	page = NULL;
 	/* CMA can be used only in the context which permits sleeping */
@@ -95,7 +92,7 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
 						 flag);
 		if (page) {
 			addr = phys_to_dma(dev, page_to_phys(page));
-			if (addr + size > dma_mask) {
+			if (addr + size > dev->coherent_dma_mask) {
 				dma_release_from_contiguous(dev, page, count);
 				page = NULL;
 			}
@@ -108,10 +105,11 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
 		return NULL;
 
 	addr = phys_to_dma(dev, page_to_phys(page));
-	if (addr + size > dma_mask) {
+	if (addr + size > dev->coherent_dma_mask) {
 		__free_pages(page, get_order(size));
 
-		if (dma_mask < DMA_BIT_MASK(32) && !(flag & GFP_DMA)) {
+		if (dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
+		    !(flag & GFP_DMA)) {
 			flag = (flag & ~GFP_DMA32) | GFP_DMA;
 			goto again;
 		}

arch/x86/mm/mem_encrypt.c

@@ -198,12 +198,10 @@ void __init sme_early_init(void)
 static void *sev_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		       gfp_t gfp, unsigned long attrs)
 {
-	unsigned long dma_mask;
 	unsigned int order;
 	struct page *page;
 	void *vaddr = NULL;
 
-	dma_mask = dma_alloc_coherent_mask(dev, gfp);
 	order = get_order(size);
 
 	/*
@@ -221,7 +219,7 @@ static void *sev_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		 * mask with it already cleared.
 		 */
 		addr = __sme_clr(phys_to_dma(dev, page_to_phys(page)));
-		if ((addr + size) > dma_mask) {
+		if ((addr + size) > dev->coherent_dma_mask) {
 			__free_pages(page, get_order(size));
 		} else {
 			vaddr = page_address(page);

drivers/xen/swiotlb-xen.c

@@ -53,20 +53,6 @@
  * API.
  */
 
-#ifndef CONFIG_X86
-static unsigned long dma_alloc_coherent_mask(struct device *dev,
-					    gfp_t gfp)
-{
-	unsigned long dma_mask = 0;
-
-	dma_mask = dev->coherent_dma_mask;
-	if (!dma_mask)
-		dma_mask = (gfp & GFP_DMA) ? DMA_BIT_MASK(24) : DMA_BIT_MASK(32);
-
-	return dma_mask;
-}
-#endif
-
 #define XEN_SWIOTLB_ERROR_CODE	(~(dma_addr_t)0x0)
 
 static char *xen_io_tlb_start, *xen_io_tlb_end;
@@ -328,7 +314,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 		return ret;
 
 	if (hwdev && hwdev->coherent_dma_mask)
-		dma_mask = dma_alloc_coherent_mask(hwdev, flags);
+		dma_mask = hwdev->coherent_dma_mask;
 
 	/* At this point dma_handle is the physical address, next we are
 	 * going to set it to the machine address.