On 2020-09-08 17:47, Christoph Hellwig wrote:
There is no harm in just always clearing the SME encryption bit, while
significantly simplifying the interface.

After a 10-minute diversion into "but hang on, force_dma_unencrypted() is meaningful on PPC and S390 too..." before realising that it all does just come back to __sme_clr(), which is indeed a no-op for everyone other than AMD, any simplification of this mess is indeed welcome :)

Unless I've massively misunderstood how SME is supposed to work,

Reviewed-by: Robin Murphy <robin.mur...@arm.com>

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
  arch/arm/include/asm/dma-direct.h      |  2 +-
  arch/mips/bmips/dma.c                  |  2 +-
  arch/mips/cavium-octeon/dma-octeon.c   |  2 +-
  arch/mips/include/asm/dma-direct.h     |  2 +-
  arch/mips/loongson2ef/fuloong-2e/dma.c |  2 +-
  arch/mips/loongson2ef/lemote-2f/dma.c  |  2 +-
  arch/mips/loongson64/dma.c             |  2 +-
  arch/mips/pci/pci-ar2315.c             |  2 +-
  arch/mips/pci/pci-xtalk-bridge.c       |  2 +-
  arch/mips/sgi-ip32/ip32-dma.c          |  2 +-
  arch/powerpc/include/asm/dma-direct.h  |  2 +-
  include/linux/dma-direct.h             | 14 +++++---------
  kernel/dma/direct.c                    |  6 +-----
  13 files changed, 17 insertions(+), 25 deletions(-)

diff --git a/arch/arm/include/asm/dma-direct.h 
b/arch/arm/include/asm/dma-direct.h
index 7c3001a6a775bf..a8cee87a93e8ab 100644
--- a/arch/arm/include/asm/dma-direct.h
+++ b/arch/arm/include/asm/dma-direct.h
@@ -8,7 +8,7 @@ static inline dma_addr_t __phys_to_dma(struct device *dev, 
phys_addr_t paddr)
        return pfn_to_dma(dev, __phys_to_pfn(paddr)) + offset;
  }
-static inline phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)
+static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
  {
        unsigned int offset = dev_addr & ~PAGE_MASK;
        return __pfn_to_phys(dma_to_pfn(dev, dev_addr)) + offset;
diff --git a/arch/mips/bmips/dma.c b/arch/mips/bmips/dma.c
index df56bf4179e347..ba2a5d33dfd3fa 100644
--- a/arch/mips/bmips/dma.c
+++ b/arch/mips/bmips/dma.c
@@ -52,7 +52,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t pa)
        return pa;
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dma_addr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
  {
        struct bmips_dma_range *r;
diff --git a/arch/mips/cavium-octeon/dma-octeon.c b/arch/mips/cavium-octeon/dma-octeon.c
index 14ea680d180e07..388b13ba2558c2 100644
--- a/arch/mips/cavium-octeon/dma-octeon.c
+++ b/arch/mips/cavium-octeon/dma-octeon.c
@@ -177,7 +177,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t 
paddr)
        return paddr;
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
  {
  #ifdef CONFIG_PCI
        if (dev && dev_is_pci(dev))
diff --git a/arch/mips/include/asm/dma-direct.h 
b/arch/mips/include/asm/dma-direct.h
index 14e352651ce946..8e178651c638c2 100644
--- a/arch/mips/include/asm/dma-direct.h
+++ b/arch/mips/include/asm/dma-direct.h
@@ -3,6 +3,6 @@
  #define _MIPS_DMA_DIRECT_H 1
dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr);
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr);
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr);
#endif /* _MIPS_DMA_DIRECT_H */
diff --git a/arch/mips/loongson2ef/fuloong-2e/dma.c 
b/arch/mips/loongson2ef/fuloong-2e/dma.c
index e122292bf6660a..83fadeb3fd7d56 100644
--- a/arch/mips/loongson2ef/fuloong-2e/dma.c
+++ b/arch/mips/loongson2ef/fuloong-2e/dma.c
@@ -6,7 +6,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
        return paddr | 0x80000000;
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dma_addr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
  {
        return dma_addr & 0x7fffffff;
  }
diff --git a/arch/mips/loongson2ef/lemote-2f/dma.c 
b/arch/mips/loongson2ef/lemote-2f/dma.c
index abf0e39d7e4696..302b43a14eee74 100644
--- a/arch/mips/loongson2ef/lemote-2f/dma.c
+++ b/arch/mips/loongson2ef/lemote-2f/dma.c
@@ -6,7 +6,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t paddr)
        return paddr | 0x80000000;
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dma_addr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
  {
        if (dma_addr > 0x8fffffff)
                return dma_addr;
diff --git a/arch/mips/loongson64/dma.c b/arch/mips/loongson64/dma.c
index dbfe6e82fddd1c..b3dc5d0bd2b113 100644
--- a/arch/mips/loongson64/dma.c
+++ b/arch/mips/loongson64/dma.c
@@ -13,7 +13,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t 
paddr)
        return ((nid << 44) ^ paddr) | (nid << node_id_offset);
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
  {
        /* We extract 2bit node id (bit 44~47, only bit 44~45 used now) from
         * Loongson-3's 48bit address space and embed it into 40bit */
diff --git a/arch/mips/pci/pci-ar2315.c b/arch/mips/pci/pci-ar2315.c
index 490953f515282a..d88395684f487d 100644
--- a/arch/mips/pci/pci-ar2315.c
+++ b/arch/mips/pci/pci-ar2315.c
@@ -175,7 +175,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t 
paddr)
        return paddr + ar2315_dev_offset(dev);
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dma_addr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
  {
        return dma_addr - ar2315_dev_offset(dev);
  }
diff --git a/arch/mips/pci/pci-xtalk-bridge.c b/arch/mips/pci/pci-xtalk-bridge.c
index 9b3cc775c55e05..f1b37f32b55395 100644
--- a/arch/mips/pci/pci-xtalk-bridge.c
+++ b/arch/mips/pci/pci-xtalk-bridge.c
@@ -33,7 +33,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t 
paddr)
        return bc->baddr + paddr;
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dma_addr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
  {
        return dma_addr & ~(0xffUL << 56);
  }
diff --git a/arch/mips/sgi-ip32/ip32-dma.c b/arch/mips/sgi-ip32/ip32-dma.c
index fa7b17cb53853e..160317294d97a9 100644
--- a/arch/mips/sgi-ip32/ip32-dma.c
+++ b/arch/mips/sgi-ip32/ip32-dma.c
@@ -27,7 +27,7 @@ dma_addr_t __phys_to_dma(struct device *dev, phys_addr_t 
paddr)
        return dma_addr;
  }
-phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dma_addr)
+phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dma_addr)
  {
        phys_addr_t paddr = dma_addr & RAM_OFFSET_MASK;
diff --git a/arch/powerpc/include/asm/dma-direct.h b/arch/powerpc/include/asm/dma-direct.h
index abc154d784b078..95b09313d2a4cf 100644
--- a/arch/powerpc/include/asm/dma-direct.h
+++ b/arch/powerpc/include/asm/dma-direct.h
@@ -7,7 +7,7 @@ static inline dma_addr_t __phys_to_dma(struct device *dev, 
phys_addr_t paddr)
        return paddr + dev->archdata.dma_offset;
  }
-static inline phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t daddr)
+static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
  {
        return daddr - dev->archdata.dma_offset;
  }
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index 20eceb2e4f91f8..f00e262ab6b154 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -24,11 +24,12 @@ static inline dma_addr_t __phys_to_dma(struct device *dev, 
phys_addr_t paddr)
        return dev_addr - ((dma_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
  }
-static inline phys_addr_t __dma_to_phys(struct device *dev, dma_addr_t dev_addr)
+static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
  {
-       phys_addr_t paddr = (phys_addr_t)dev_addr;
+       phys_addr_t paddr = (phys_addr_t)dev_addr +
+               ((phys_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
- return paddr + ((phys_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
+       return __sme_clr(paddr);
  }
  #endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */
@@ -44,7 +45,7 @@ static inline bool force_dma_unencrypted(struct device *dev)
  /*
   * If memory encryption is supported, phys_to_dma will set the memory 
encryption
   * bit in the DMA address, and dma_to_phys will clear it.  The raw 
__phys_to_dma
- * and __dma_to_phys versions should only be used on non-encrypted memory for
+ * version should only be used on non-encrypted memory for
   * special occasions like DMA coherent buffers.
   */
  static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
@@ -52,11 +53,6 @@ static inline dma_addr_t phys_to_dma(struct device *dev, 
phys_addr_t paddr)
        return __sme_set(__phys_to_dma(dev, paddr));
  }
-static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
-{
-       return __sme_clr(__dma_to_phys(dev, daddr));
-}
-
  static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t 
size,
                bool is_ram)
  {
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 57a6e7d7cf8f16..bfb479c8a370fa 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -48,11 +48,6 @@ static gfp_t dma_direct_optimal_gfp_mask(struct device *dev, 
u64 dma_mask,
  {
        u64 dma_limit = min_not_zero(dma_mask, dev->bus_dma_limit);
- if (force_dma_unencrypted(dev))
-               *phys_limit = __dma_to_phys(dev, dma_limit);
-       else
-               *phys_limit = dma_to_phys(dev, dma_limit);
-
        /*
         * Optimistically try the zone that the physical address mask falls
         * into first.  If that returns memory that isn't actually addressable
@@ -61,6 +56,7 @@ static gfp_t dma_direct_optimal_gfp_mask(struct device *dev, 
u64 dma_mask,
         * Note that GFP_DMA32 and GFP_DMA are no ops without the corresponding
         * zones.
         */
+       *phys_limit = dma_to_phys(dev, dma_limit);
        if (*phys_limit <= DMA_BIT_MASK(zone_dma_bits))
                return GFP_DMA;
        if (*phys_limit <= DMA_BIT_MASK(32))

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