[PATCH v5 22/32] x86, swiotlb: DMA support for memory encryption

Tom Lendacky
2017-04-18T21:20:38Z

Since DMA addresses will effectively look like 48-bit addresses when the
memory encryption mask is set, SWIOTLB is needed if the DMA mask of the
device performing the DMA does not support 48-bits. SWIOTLB will be
initialized to create decrypted bounce buffers for use by these devices.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
arch/x86/include/asm/dma-mapping.h | 5 ++-
arch/x86/include/asm/mem_encrypt.h | 5 +++
arch/x86/kernel/pci-dma.c | 11 +++++--
arch/x86/kernel/pci-nommu.c | 2 +
arch/x86/kernel/pci-swiotlb.c | 8 ++++-
arch/x86/mm/mem_encrypt.c | 22 ++++++++++++++
include/linux/mem_encrypt.h | 10 ++++++
include/linux/swiotlb.h | 1 +
init/main.c | 13 ++++++++
lib/swiotlb.c | 56 +++++++++++++++++++++++++++++++-----
10 files changed, 116 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
index 08a0838..d75430a 100644
--- a/arch/x86/include/asm/dma-mapping.h
+++ b/arch/x86/include/asm/dma-mapping.h
@@ -12,6 +12,7 @@
#include <asm/io.h>
#include <asm/swiotlb.h>
#include <linux/dma-contiguous.h>
+#include <asm/mem_encrypt.h>

#ifdef CONFIG_ISA
# define ISA_DMA_BIT_MASK DMA_BIT_MASK(24)
@@ -62,12 +63,12 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)

static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
{
- return paddr;
+ return __sme_set(paddr);
}

static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
{
- return daddr;
+ return __sme_clr(daddr);
}
#endif /* CONFIG_X86_DMA_REMAP */

diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
index 130d7fe..0637b4b 100644
--- a/arch/x86/include/asm/mem_encrypt.h
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -36,6 +36,11 @@ void __init sme_early_decrypt(resource_size_t paddr,

void __init sme_early_init(void);

+/* Architecture __weak replacement functions */
+void __init mem_encrypt_init(void);
+
+void swiotlb_set_mem_attributes(void *vaddr, unsigned long size);
+
#else /* !CONFIG_AMD_MEM_ENCRYPT */

#ifndef sme_me_mask
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 3a216ec..72d96d4 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -93,9 +93,12 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
if (gfpflags_allow_blocking(flag)) {
page = dma_alloc_from_contiguous(dev, count, get_order(size),
flag);
- if (page && page_to_phys(page) + size > dma_mask) {
- dma_release_from_contiguous(dev, page, count);
- page = NULL;
+ if (page) {
+ addr = phys_to_dma(dev, page_to_phys(page));
+ if (addr + size > dma_mask) {
+ dma_release_from_contiguous(dev, page, count);
+ page = NULL;
+ }
}
}
/* fallback */
@@ -104,7 +107,7 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
if (!page)
return NULL;

- addr = page_to_phys(page);
+ addr = phys_to_dma(dev, page_to_phys(page));
if (addr + size > dma_mask) {
__free_pages(page, get_order(size));

diff --git a/arch/x86/kernel/pci-nommu.c b/arch/x86/kernel/pci-nommu.c
index a88952e..98b576a 100644
--- a/arch/x86/kernel/pci-nommu.c
+++ b/arch/x86/kernel/pci-nommu.c
@@ -30,7 +30,7 @@ static dma_addr_t nommu_map_page(struct device *dev, struct page *page,
enum dma_data_direction dir,
unsigned long attrs)
{
- dma_addr_t bus = page_to_phys(page) + offset;
+ dma_addr_t bus = phys_to_dma(dev, page_to_phys(page)) + offset;
WARN_ON(size == 0);
if (!check_addr("map_single", dev, bus, size))
return DMA_ERROR_CODE;
diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index 1e23577..a75fee7 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -12,6 +12,8 @@
#include <asm/dma.h>
#include <asm/xen/swiotlb-xen.h>
#include <asm/iommu_table.h>
+#include <asm/mem_encrypt.h>
+
int swiotlb __read_mostly;

void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
@@ -64,11 +66,13 @@ void x86_swiotlb_free_coherent(struct device *dev, size_t size,
* pci_swiotlb_detect_override - set swiotlb to 1 if necessary
*
* This returns non-zero if we are forced to use swiotlb (by the boot
- * option).
+ * option). If memory encryption is enabled then swiotlb will be set
+ * to 1 so that bounce buffers are allocated and used for devices that
+ * do not support the addressing range required for the encryption mask.
*/
int __init pci_swiotlb_detect_override(void)
{
- if (swiotlb_force == SWIOTLB_FORCE)
+ if ((swiotlb_force == SWIOTLB_FORCE) || sme_active())
swiotlb = 1;

return swiotlb;
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 2321f05..30b07a3 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -16,11 +16,14 @@
#ifdef CONFIG_AMD_MEM_ENCRYPT

#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+#include <linux/swiotlb.h>

#include <asm/tlbflush.h>
#include <asm/fixmap.h>
#include <asm/setup.h>
#include <asm/bootparam.h>
+#include <asm/cacheflush.h>

/*
* Since SME related variables are set early in the boot process they must
@@ -194,6 +197,25 @@ void __init sme_early_init(void)
protection_map[i] = pgprot_encrypted(protection_map[i]);
}

+/* Architecture __weak replacement functions */
+void __init mem_encrypt_init(void)
+{
+ if (!sme_me_mask)
+ return;
+
+ /* Call into SWIOTLB to update the SWIOTLB DMA buffers */
+ swiotlb_update_mem_attributes();
+}
+
+void swiotlb_set_mem_attributes(void *vaddr, unsigned long size)
+{
+ WARN(PAGE_ALIGN(size) != size,
+ "size is not page-aligned (%#lx)\n", size);
+
+ /* Make the SWIOTLB buffer area decrypted */
+ set_memory_decrypted((unsigned long)vaddr, size >> PAGE_SHIFT);
+}
+
void __init sme_encrypt_kernel(void)
{
}
diff --git a/include/linux/mem_encrypt.h b/include/linux/mem_encrypt.h
index 14a7b9f..3c384d1 100644
--- a/include/linux/mem_encrypt.h
+++ b/include/linux/mem_encrypt.h
@@ -32,6 +32,16 @@ static inline bool sme_active(void)

#endif /* CONFIG_AMD_MEM_ENCRYPT */

+#ifndef __sme_set
+/*
+ * The __sme_set() and __sme_clr() macros are useful for adding or removing
+ * the encryption mask from a value (e.g. when dealing with pagetable
+ * entries).
+ */
+#define __sme_set(x) ((unsigned long)(x) | sme_me_mask)
+#define __sme_clr(x) ((unsigned long)(x) & ~sme_me_mask)
+#endif
+
#endif /* __ASSEMBLY__ */

#endif /* __MEM_ENCRYPT_H__ */
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 4ee479f..15e7160 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -35,6 +35,7 @@ enum swiotlb_force {
extern unsigned long swiotlb_nr_tbl(void);
unsigned long swiotlb_size_or_default(void);
extern int swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs);
+extern void __init swiotlb_update_mem_attributes(void);

/*
* Enumeration for sync targets
diff --git a/init/main.c b/init/main.c
index b0c11cb..e5b4fb7 100644
--- a/init/main.c
+++ b/init/main.c
@@ -467,6 +467,10 @@ void __init __weak thread_stack_cache_init(void)
}
#endif

+void __init __weak mem_encrypt_init(void)
+{
+}
+
/*
* Set up kernel memory allocators
*/
@@ -614,6 +618,15 @@ asmlinkage __visible void __init start_kernel(void)
*/
locking_selftest();

+ /*
+ * This needs to be called before any devices perform DMA
+ * operations that might use the SWIOTLB bounce buffers.
+ * This call will mark the bounce buffers as decrypted so
+ * that their usage will not cause "plain-text" data to be
+ * decrypted when accessed.
+ */
+ mem_encrypt_init();
+
#ifdef CONFIG_BLK_DEV_INITRD
if (initrd_start && !initrd_below_start_ok &&
page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index a8d74a7..74d6557 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -30,6 +30,7 @@
#include <linux/highmem.h>
#include <linux/gfp.h>
#include <linux/scatterlist.h>
+#include <linux/mem_encrypt.h>

#include <asm/io.h>
#include <asm/dma.h>
@@ -155,6 +156,17 @@ unsigned long swiotlb_size_or_default(void)
return size ? size : (IO_TLB_DEFAULT_SIZE);
}

+void __weak swiotlb_set_mem_attributes(void *vaddr, unsigned long size)
+{
+}
+
+/* For swiotlb, clear memory encryption mask from dma addresses */
+static dma_addr_t swiotlb_phys_to_dma(struct device *hwdev,
+ phys_addr_t address)
+{
+ return __sme_clr(phys_to_dma(hwdev, address));
+}
+
/* Note that this doesn't work with highmem page */
static dma_addr_t swiotlb_virt_to_bus(struct device *hwdev,
volatile void *address)
@@ -183,6 +195,31 @@ void swiotlb_print_info(void)
bytes >> 20, vstart, vend - 1);
}

+/*
+ * Early SWIOTLB allocation may be too early to allow an architecture to
+ * perform the desired operations. This function allows the architecture to
+ * call SWIOTLB when the operations are possible. It needs to be called
+ * before the SWIOTLB memory is used.
+ */
+void __init swiotlb_update_mem_attributes(void)
+{
+ void *vaddr;
+ unsigned long bytes;
+
+ if (no_iotlb_memory || late_alloc)
+ return;
+
+ vaddr = phys_to_virt(io_tlb_start);
+ bytes = PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT);
+ swiotlb_set_mem_attributes(vaddr, bytes);
+ memset(vaddr, 0, bytes);
+
+ vaddr = phys_to_virt(io_tlb_overflow_buffer);
+ bytes = PAGE_ALIGN(io_tlb_overflow);
+ swiotlb_set_mem_attributes(vaddr, bytes);
+ memset(vaddr, 0, bytes);
+}
+
int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
{
void *v_overflow_buffer;
@@ -320,6 +357,7 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
io_tlb_start = virt_to_phys(tlb);
io_tlb_end = io_tlb_start + bytes;

+ swiotlb_set_mem_attributes(tlb, bytes);
memset(tlb, 0, bytes);

/*
@@ -330,6 +368,8 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
if (!v_overflow_buffer)
goto cleanup2;

+ swiotlb_set_mem_attributes(v_overflow_buffer, io_tlb_overflow);
+ memset(v_overflow_buffer, 0, io_tlb_overflow);
io_tlb_overflow_buffer = virt_to_phys(v_overflow_buffer);

/*
@@ -581,7 +621,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
return SWIOTLB_MAP_ERROR;
}

- start_dma_addr = phys_to_dma(hwdev, io_tlb_start);
+ start_dma_addr = swiotlb_phys_to_dma(hwdev, io_tlb_start);
return swiotlb_tbl_map_single(hwdev, start_dma_addr, phys, size,
dir, attrs);
}
@@ -702,7 +742,7 @@ void swiotlb_tbl_sync_single(struct device *hwdev, phys_addr_t tlb_addr,
goto err_warn;

ret = phys_to_virt(paddr);
- dev_addr = phys_to_dma(hwdev, paddr);
+ dev_addr = swiotlb_phys_to_dma(hwdev, paddr);

/* Confirm address can be DMA'd by device */
if (dev_addr + size - 1 > dma_mask) {
@@ -812,10 +852,10 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
map = map_single(dev, phys, size, dir, attrs);
if (map == SWIOTLB_MAP_ERROR) {
swiotlb_full(dev, size, dir, 1);
- return phys_to_dma(dev, io_tlb_overflow_buffer);
+ return swiotlb_phys_to_dma(dev, io_tlb_overflow_buffer);
}

- dev_addr = phys_to_dma(dev, map);
+ dev_addr = swiotlb_phys_to_dma(dev, map);

/* Ensure that the address returned is DMA'ble */
if (dma_capable(dev, dev_addr, size))
@@ -824,7 +864,7 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
attrs |= DMA_ATTR_SKIP_CPU_SYNC;
swiotlb_tbl_unmap_single(dev, map, size, dir, attrs);

- return phys_to_dma(dev, io_tlb_overflow_buffer);
+ return swiotlb_phys_to_dma(dev, io_tlb_overflow_buffer);
}
EXPORT_SYMBOL_GPL(swiotlb_map_page);

@@ -958,7 +998,7 @@ void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
sg_dma_len(sgl) = 0;
return 0;
}
- sg->dma_address = phys_to_dma(hwdev, map);
+ sg->dma_address = swiotlb_phys_to_dma(hwdev, map);
} else
sg->dma_address = dev_addr;
sg_dma_len(sg) = sg->length;
@@ -1026,7 +1066,7 @@ void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
int
swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
{
- return (dma_addr == phys_to_dma(hwdev, io_tlb_overflow_buffer));
+ return (dma_addr == swiotlb_phys_to_dma(hwdev, io_tlb_overflow_buffer));
}
EXPORT_SYMBOL(swiotlb_dma_mapping_error);

@@ -1039,6 +1079,6 @@ void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
int
swiotlb_dma_supported(struct device *hwdev, u64 mask)
{
- return phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
+ return swiotlb_phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
}
EXPORT_SYMBOL(swiotlb_dma_supported);