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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 fafadcd165 ("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: fafadcd165 ("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>
This commit is contained in:
Tom Lendacky 2019-07-10 19:01:19 +00:00 committed by Christoph Hellwig
parent 9637d51734
commit 9087c37584
7 changed files with 54 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/s390/Kconfig
View File

@ -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

7
arch/s390/mm/init.c
View File

@ -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)
{

1
arch/x86/Kconfig
View File

@ -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

30
arch/x86/mm/mem_encrypt.c
View File

@ -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)
{

9
include/linux/dma-direct.h
View File

@ -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

3
kernel/dma/Kconfig
View File

@ -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

16
kernel/dma/direct.c
View File

@ -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) &&