dma/direct: Handle force decryption for DMA coherent buffers in common code

With that in place the generic DMA-direct routines can be used to
allocate non-encrypted bounce buffers, and the x86 SEV case can use
the generic swiotlb ops including nice features such as using CMA
allocations.

Note that I'm not too happy about using sev_active() in DMA-direct, but
I couldn't come up with a good enough name for a wrapper to make it
worth adding.

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Jon Mason <jdmason@kudzu.us>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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/20180319103826.12853-14-hch@lst.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 26 insertions, 6 deletions

diff --git a/lib/dma-direct.c b/lib/dma-direct.c
index c9e8e21cb334..1277d293d4da 100644
--- a/lib/dma-direct.c
+++ b/lib/dma-direct.c
@@ -9,6 +9,7 @@
 #include <linux/scatterlist.h>
 #include <linux/dma-contiguous.h>
 #include <linux/pfn.h>
+#include <linux/set_memory.h>
 
 #define DIRECT_MAPPING_ERROR            0
 
@@ -20,6 +21,14 @@
 #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 bool
 check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
                 const char *caller)
@@ -37,7 +46,9 @@ check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
 
 static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
 {
-        return phys_to_dma(dev, phys) + size - 1 <= dev->coherent_dma_mask;
+        dma_addr_t addr = force_dma_unencrypted() ?
+                __phys_to_dma(dev, phys) : phys_to_dma(dev, phys);
+        return addr + size - 1 <= dev->coherent_dma_mask;
 }
 
 void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
@@ -46,6 +57,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
         unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
         int page_order = get_order(size);
         struct page *page = NULL;
+        void *ret;
 
         /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
         if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
@@ -78,10 +90,15 @@ again:
 
         if (!page)
                 return NULL;
-
-        *dma_handle = phys_to_dma(dev, page_to_phys(page));
-        memset(page_address(page), 0, size);
-        return page_address(page);
+        ret = page_address(page);
+        if (force_dma_unencrypted()) {
+                set_memory_decrypted((unsigned long)ret, 1 << page_order);
+                *dma_handle = __phys_to_dma(dev, page_to_phys(page));
+        } else {
+                *dma_handle = phys_to_dma(dev, page_to_phys(page));
+        }
+        memset(ret, 0, size);
+        return ret;
 }
 
 /*
@@ -92,9 +109,12 @@ void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
                 dma_addr_t dma_addr, unsigned long attrs)
 {
         unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+        unsigned int page_order = get_order(size);
 
+        if (force_dma_unencrypted())
+                set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);
         if (!dma_release_from_contiguous(dev, virt_to_page(cpu_addr), count))
-                free_pages((unsigned long)cpu_addr, get_order(size));
+                free_pages((unsigned long)cpu_addr, page_order);
 }
 
 static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,