[Xen-devel] [PATCH 17/24] x86/amd_gart: remove the mapping_error dma_map_ops method

[Christoph Hellwig <hch@xxxxxx>]

Return DMA_MAPPING_ERROR instead of the magic bad_dma_addr on a dma
mapping failure and let the core dma-mapping code handle the rest.

Remove the magic EMERGENCY_PAGES that the bad_dma_addr gets redirected to.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 arch/x86/kernel/amd_gart_64.c | 39 ++++++-----------------------------
 1 file changed, 6 insertions(+), 33 deletions(-)

diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index 3f9d1b4019bb..4e733de93f41 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -50,8 +50,6 @@ static unsigned long iommu_pages;     /* .. and in pages */
 
 static u32 *iommu_gatt_base;           /* Remapping table */
 
-static dma_addr_t bad_dma_addr;
-
 /*
  * If this is disabled the IOMMU will use an optimized flushing strategy
  * of only flushing when an mapping is reused. With it true the GART is
@@ -74,8 +72,6 @@ static u32 gart_unmapped_entry;
        (((x) & 0xfffff000) | (((x) >> 32) << 4) | GPTE_VALID | GPTE_COHERENT)
 #define GPTE_DECODE(x) (((x) & 0xfffff000) | (((u64)(x) & 0xff0) << 28))
 
-#define EMERGENCY_PAGES 32 /* = 128KB */
-
 #ifdef CONFIG_AGP
 #define AGPEXTERN extern
 #else
@@ -184,14 +180,6 @@ static void iommu_full(struct device *dev, size_t size, 
int dir)
         */
 
        dev_err(dev, "PCI-DMA: Out of IOMMU space for %lu bytes\n", size);
-
-       if (size > PAGE_SIZE*EMERGENCY_PAGES) {
-               if (dir == PCI_DMA_FROMDEVICE || dir == PCI_DMA_BIDIRECTIONAL)
-                       panic("PCI-DMA: Memory would be corrupted\n");
-               if (dir == PCI_DMA_TODEVICE || dir == PCI_DMA_BIDIRECTIONAL)
-                       panic(KERN_ERR
-                               "PCI-DMA: Random memory would be DMAed\n");
-       }
 #ifdef CONFIG_IOMMU_LEAK
        dump_leak();
 #endif
@@ -220,7 +208,7 @@ static dma_addr_t dma_map_area(struct device *dev, 
dma_addr_t phys_mem,
        int i;
 
        if (unlikely(phys_mem + size > GART_MAX_PHYS_ADDR))
-               return bad_dma_addr;
+               return DMA_MAPPING_ERROR;
 
        iommu_page = alloc_iommu(dev, npages, align_mask);
        if (iommu_page == -1) {
@@ -229,7 +217,7 @@ static dma_addr_t dma_map_area(struct device *dev, 
dma_addr_t phys_mem,
                if (panic_on_overflow)
                        panic("dma_map_area overflow %lu bytes\n", size);
                iommu_full(dev, size, dir);
-               return bad_dma_addr;
+               return DMA_MAPPING_ERROR;
        }
 
        for (i = 0; i < npages; i++) {
@@ -271,7 +259,7 @@ static void gart_unmap_page(struct device *dev, dma_addr_t 
dma_addr,
        int npages;
        int i;
 
-       if (dma_addr < iommu_bus_base + EMERGENCY_PAGES*PAGE_SIZE ||
+       if (dma_addr == DMA_MAPPING_ERROR ||
            dma_addr >= iommu_bus_base + iommu_size)
                return;
 
@@ -315,7 +303,7 @@ static int dma_map_sg_nonforce(struct device *dev, struct 
scatterlist *sg,
 
                if (nonforced_iommu(dev, addr, s->length)) {
                        addr = dma_map_area(dev, addr, s->length, dir, 0);
-                       if (addr == bad_dma_addr) {
+                       if (addr == DMA_MAPPING_ERROR) {
                                if (i > 0)
                                        gart_unmap_sg(dev, sg, i, dir, 0);
                                nents = 0;
@@ -471,7 +459,7 @@ static int gart_map_sg(struct device *dev, struct 
scatterlist *sg, int nents,
 
        iommu_full(dev, pages << PAGE_SHIFT, dir);
        for_each_sg(sg, s, nents, i)
-               s->dma_address = bad_dma_addr;
+               s->dma_address = DMA_MAPPING_ERROR;
        return 0;
 }
 
@@ -490,7 +478,7 @@ gart_alloc_coherent(struct device *dev, size_t size, 
dma_addr_t *dma_addr,
        *dma_addr = dma_map_area(dev, virt_to_phys(vaddr), size,
                        DMA_BIDIRECTIONAL, (1UL << get_order(size)) - 1);
        flush_gart();
-       if (unlikely(*dma_addr == bad_dma_addr))
+       if (unlikely(*dma_addr == DMA_MAPPING_ERROR))
                goto out_free;
        return vaddr;
 out_free:
@@ -507,11 +495,6 @@ gart_free_coherent(struct device *dev, size_t size, void 
*vaddr,
        dma_direct_free_pages(dev, size, vaddr, dma_addr, attrs);
 }
 
-static int gart_mapping_error(struct device *dev, dma_addr_t dma_addr)
-{
-       return (dma_addr == bad_dma_addr);
-}
-
 static int no_agp;
 
 static __init unsigned long check_iommu_size(unsigned long aper, u64 aper_size)
@@ -695,7 +678,6 @@ static const struct dma_map_ops gart_dma_ops = {
        .unmap_page                     = gart_unmap_page,
        .alloc                          = gart_alloc_coherent,
        .free                           = gart_free_coherent,
-       .mapping_error                  = gart_mapping_error,
        .dma_supported                  = dma_direct_supported,
 };
 
@@ -784,19 +766,12 @@ int __init gart_iommu_init(void)
        }
 #endif
 
-       /*
-        * Out of IOMMU space handling.
-        * Reserve some invalid pages at the beginning of the GART.
-        */
-       bitmap_set(iommu_gart_bitmap, 0, EMERGENCY_PAGES);
-
        pr_info("PCI-DMA: Reserving %luMB of IOMMU area in the AGP aperture\n",
               iommu_size >> 20);
 
        agp_memory_reserved     = iommu_size;
        iommu_start             = aper_size - iommu_size;
        iommu_bus_base          = info.aper_base + iommu_start;
-       bad_dma_addr            = iommu_bus_base;
        iommu_gatt_base         = agp_gatt_table + (iommu_start>>PAGE_SHIFT);
 
        /*
@@ -838,8 +813,6 @@ int __init gart_iommu_init(void)
        if (!scratch)
                panic("Cannot allocate iommu scratch page");
        gart_unmapped_entry = GPTE_ENCODE(__pa(scratch));
-       for (i = EMERGENCY_PAGES; i < iommu_pages; i++)
-               iommu_gatt_base[i] = gart_unmapped_entry;
 
        flush_gart();
        dma_ops = &gart_dma_ops;
-- 
2.19.1


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