dma-direct: Force unencrypted DMA under SME for certain DMA masks

If a device doesn't support DMA to a physical address that includes the
encryption bit (currently bit 47, so 48-bit DMA), then the DMA must
occur to unencrypted memory. SWIOTLB is used to satisfy that requirement
if an IOMMU is not active (enabled or configured in passthrough mode).

However, commit fafadcd16595 ("swiotlb: don't dip into swiotlb pool for
coherent allocations") modified the coherent allocation support in
SWIOTLB to use the DMA direct coherent allocation support. When an IOMMU
is not active, this resulted in dma_alloc_coherent() failing for devices
that didn't support DMA addresses that included the encryption bit.

Addressing this requires changes to the force_dma_unencrypted() function
in kernel/dma/direct.c. Since the function is now non-trivial and
SME/SEV specific, update the DMA direct support to add an arch override
for the force_dma_unencrypted() function. The arch override is selected
when CONFIG_AMD_MEM_ENCRYPT is set. The arch override function resides in
the arch/x86/mm/mem_encrypt.c file and forces unencrypted DMA when either
SEV is active or SME is active and the device does not support DMA to
physical addresses that include the encryption bit.

Fixes: fafadcd16595 ("swiotlb: don't dip into swiotlb pool for coherent allocations")
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
[hch: moved the force_dma_unencrypted declaration to dma-mapping.h,
      fold the s390 fix from Halil Pasic]
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 5d8570e..a4ad273 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -189,6 +189,7 @@ config S390
        select VIRT_CPU_ACCOUNTING
        select ARCH_HAS_SCALED_CPUTIME
        select HAVE_NMI
+       select ARCH_HAS_FORCE_DMA_UNENCRYPTED
        select SWIOTLB
        select GENERIC_ALLOCATOR
 

diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
index f0bee6a..78c319c 100644 (file)
--- a/arch/s390/mm/init.c
+++ b/arch/s390/mm/init.c
@@ -30,7 +30,7 @@
 #include <linux/export.h>
 #include <linux/cma.h>
 #include <linux/gfp.h>
-#include <linux/dma-mapping.h>
+#include <linux/dma-direct.h>
 #include <asm/processor.h>
 #include <linux/uaccess.h>
 #include <asm/pgtable.h>
@@ -161,6 +161,11 @@ bool sev_active(void)
        return is_prot_virt_guest();
 }
 
+bool force_dma_unencrypted(struct device *dev)
+{
+       return sev_active();
+}
+
 /* protected virtualization */
 static void pv_init(void)
 {

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8797413..d1afe92 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1528,6 +1528,7 @@ config AMD_MEM_ENCRYPT
        depends on X86_64 && CPU_SUP_AMD
        select DYNAMIC_PHYSICAL_MASK
        select ARCH_USE_MEMREMAP_PROT
+       select ARCH_HAS_FORCE_DMA_UNENCRYPTED
        ---help---
          Say yes to enable support for the encryption of system memory.
          This requires an AMD processor that supports Secure Memory

diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index e0df96f..c805f0a 100644 (file)
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -15,6 +15,10 @@
 #include <linux/dma-direct.h>
 #include <linux/swiotlb.h>
 #include <linux/mem_encrypt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/bitops.h>
+#include <linux/dma-mapping.h>
 
 #include <asm/tlbflush.h>
 #include <asm/fixmap.h>
@@ -348,6 +352,32 @@ bool sev_active(void)
 }
 EXPORT_SYMBOL(sev_active);
 
+/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
+bool force_dma_unencrypted(struct device *dev)
+{
+       /*
+        * For SEV, all DMA must be to unencrypted addresses.
+        */
+       if (sev_active())
+               return true;
+
+       /*
+        * For SME, all DMA must be to unencrypted addresses if the
+        * device does not support DMA to addresses that include the
+        * encryption mask.
+        */
+       if (sme_active()) {
+               u64 dma_enc_mask = DMA_BIT_MASK(__ffs64(sme_me_mask));
+               u64 dma_dev_mask = min_not_zero(dev->coherent_dma_mask,
+                                               dev->bus_dma_mask);
+
+               if (dma_dev_mask <= dma_enc_mask)
+                       return true;
+       }
+
+       return false;
+}
+
 /* Architecture __weak replacement functions */
 void __init mem_encrypt_free_decrypted_mem(void)
 {

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index b733870..adf993a 100644 (file)
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -32,6 +32,15 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
 }
 #endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */
 
+#ifdef CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED
+bool force_dma_unencrypted(struct device *dev);
+#else
+static inline bool force_dma_unencrypted(struct device *dev)
+{
+       return false;
+}
+#endif /* CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED */
+
 /*
  * 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

diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 70f8f8d..9decbba 100644 (file)
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -48,6 +48,9 @@ config ARCH_HAS_DMA_COHERENT_TO_PFN
 config ARCH_HAS_DMA_MMAP_PGPROT
        bool
 
+config ARCH_HAS_FORCE_DMA_UNENCRYPTED
+       bool
+
 config DMA_NONCOHERENT_CACHE_SYNC
        bool
 

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index b90e1ae..d7cec86 100644 (file)
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -23,14 +23,6 @@
 #define ARCH_ZONE_DMA_BITS 24
 #endif
 
-/*
- * For AMD SEV all DMA must be to unencrypted addresses.
- */
-static inline bool force_dma_unencrypted(void)
-{
-       return sev_active();
-}
-
 static void report_addr(struct device *dev, dma_addr_t dma_addr, size_t size)
 {
        if (!dev->dma_mask) {
@@ -46,7 +38,7 @@ static void report_addr(struct device *dev, dma_addr_t dma_addr, size_t size)
 static inline dma_addr_t phys_to_dma_direct(struct device *dev,
                phys_addr_t phys)
 {
-       if (force_dma_unencrypted())
+       if (force_dma_unencrypted(dev))
                return __phys_to_dma(dev, phys);
        return phys_to_dma(dev, phys);
 }
@@ -67,7 +59,7 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
        if (dev->bus_dma_mask && dev->bus_dma_mask < dma_mask)
                dma_mask = dev->bus_dma_mask;
 
-       if (force_dma_unencrypted())
+       if (force_dma_unencrypted(dev))
                *phys_mask = __dma_to_phys(dev, dma_mask);
        else
                *phys_mask = dma_to_phys(dev, dma_mask);
@@ -159,7 +151,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
        }
 
        ret = page_address(page);
-       if (force_dma_unencrypted()) {
+       if (force_dma_unencrypted(dev)) {
                set_memory_decrypted((unsigned long)ret, 1 << get_order(size));
                *dma_handle = __phys_to_dma(dev, page_to_phys(page));
        } else {
@@ -192,7 +184,7 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
                return;
        }
 
-       if (force_dma_unencrypted())
+       if (force_dma_unencrypted(dev))
                set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);
 
        if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&