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Subject[rfc 5/6] dma-direct: atomic allocations must come from unencrypted pools
When AMD memory encryption is enabled, all non-blocking DMA allocations
must originate from the atomic pools depending on the device and the gfp
mask of the allocation.

Keep all memory in these pools unencrypted.

Signed-off-by: David Rientjes <rientjes@google.com>
---
arch/x86/Kconfig | 1 +
kernel/dma/direct.c | 9 ++++-----
kernel/dma/remap.c | 2 ++
3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1523,6 +1523,7 @@ config X86_CPA_STATISTICS
config AMD_MEM_ENCRYPT
bool "AMD Secure Memory Encryption (SME) support"
depends on X86_64 && CPU_SUP_AMD
+ select DMA_DIRECT_REMAP
select DYNAMIC_PHYSICAL_MASK
select ARCH_USE_MEMREMAP_PROT
select ARCH_HAS_FORCE_DMA_UNENCRYPTED
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -125,7 +125,6 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
void *ret;

if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
- dma_alloc_need_uncached(dev, attrs) &&
!gfpflags_allow_blocking(gfp)) {
ret = dma_alloc_from_pool(dev, PAGE_ALIGN(size), &page, gfp);
if (!ret)
@@ -202,6 +201,10 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
{
unsigned int page_order = get_order(size);

+ if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
+ dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
+ return;
+
if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
!force_dma_unencrypted(dev)) {
/* cpu_addr is a struct page cookie, not a kernel address */
@@ -209,10 +212,6 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
return;
}

- if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
- dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
- return;
-
if (force_dma_unencrypted(dev))
set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);

diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -8,6 +8,7 @@
#include <linux/dma-contiguous.h>
#include <linux/init.h>
#include <linux/genalloc.h>
+#include <linux/set_memory.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
@@ -141,6 +142,7 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
if (!addr)
goto free_page;

+ set_memory_decrypted((unsigned long)page_to_virt(page), nr_pages);
ret = gen_pool_add_virt(pool, (unsigned long)addr, page_to_phys(page),
pool_size, NUMA_NO_NODE);
if (ret)
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