[PATCH V2 11/14] x86/Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM

Tianyu Lan
2021-08-04T18:46:24Z

In Isolation VM with AMD SEV, bounce buffer needs to be accessed via
extra address space which is above shared_gpa_boundary
(E.G 39 bit address line) reported by Hyper-V CPUID ISOLATION_CONFIG.
The access physical address will be original physical address +
shared_gpa_boundary. The shared_gpa_boundary in the AMD SEV SNP
spec is called virtual top of memory(vTOM). Memory addresses below
vTOM are automatically treated as private while memory above
vTOM is treated as shared.

Use dma_map_decrypted() in the swiotlb code, store remap address returned
and use the remap address to copy data from/to swiotlb bounce buffer.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
Change since v1:
* Make swiotlb_init_io_tlb_mem() return error code and return
error when dma_map_decrypted() fails.

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
include/linux/swiotlb.h | 4 ++++
kernel/dma/swiotlb.c | 32 ++++++++++++++++++++++++--------
2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index f507e3eacbea..584560ecaa8e 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -72,6 +72,9 @@ extern enum swiotlb_force swiotlb_force;
* @end: The end address of the swiotlb memory pool. Used to do a quick
* range check to see if the memory was in fact allocated by this
* API.
+ * @vaddr: The vaddr of the swiotlb memory pool. The swiotlb
+ * memory pool may be remapped in the memory encrypted case and store
+ * virtual address for bounce buffer operation.
* @nslabs: The number of IO TLB blocks (in groups of 64) between @start and
* @end. For default swiotlb, this is command line adjustable via
* setup_io_tlb_npages.
@@ -89,6 +92,7 @@ extern enum swiotlb_force swiotlb_force;
struct io_tlb_mem {
phys_addr_t start;
phys_addr_t end;
+ void *vaddr;
unsigned long nslabs;
unsigned long used;
unsigned int index;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 1fa81c096c1d..29b6d888ef3b 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -176,7 +176,7 @@ void __init swiotlb_update_mem_attributes(void)
memset(vaddr, 0, bytes);
}

-static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
+static int swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
unsigned long nslabs, bool late_alloc)
{
void *vaddr = phys_to_virt(start);
@@ -194,14 +194,21 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
mem->slots[i].alloc_size = 0;
}

- set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
- memset(vaddr, 0, bytes);
+ mem->vaddr = dma_map_decrypted(vaddr, bytes);
+ if (!mem->vaddr) {
+ pr_err("Failed to decrypt memory.\n");
+ return -ENOMEM;
+ }
+
+ memset(mem->vaddr, 0, bytes);
+ return 0;
}

int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
{
struct io_tlb_mem *mem;
size_t alloc_size;
+ int ret;

if (swiotlb_force == SWIOTLB_NO_FORCE)
return 0;
@@ -216,7 +223,11 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
panic("%s: Failed to allocate %zu bytes align=0x%lx\n",
__func__, alloc_size, PAGE_SIZE);

- swiotlb_init_io_tlb_mem(mem, __pa(tlb), nslabs, false);
+ ret = swiotlb_init_io_tlb_mem(mem, __pa(tlb), nslabs, false);
+ if (ret) {
+ memblock_free(__pa(mem), alloc_size);
+ return ret;
+ }

io_tlb_default_mem = mem;
if (verbose)
@@ -304,6 +315,8 @@ int
swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
{
struct io_tlb_mem *mem;
+ int size = get_order(struct_size(mem, slots, nslabs));
+ int ret;

if (swiotlb_force == SWIOTLB_NO_FORCE)
return 0;
@@ -312,12 +325,15 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
if (WARN_ON_ONCE(io_tlb_default_mem))
return -ENOMEM;

- mem = (void *)__get_free_pages(GFP_KERNEL,
- get_order(struct_size(mem, slots, nslabs)));
+ mem = (void *)__get_free_pages(GFP_KERNEL, size);
if (!mem)
return -ENOMEM;

- swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);
+ ret = swiotlb_init_io_tlb_mem(mem, virt_to_phys(tlb), nslabs, true);
+ if (ret) {
+ free_pages((unsigned long)mem, size);
+ return ret;
+ }

io_tlb_default_mem = mem;
swiotlb_print_info();
@@ -360,7 +376,7 @@ static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size
phys_addr_t orig_addr = mem->slots[index].orig_addr;
size_t alloc_size = mem->slots[index].alloc_size;
unsigned long pfn = PFN_DOWN(orig_addr);
- unsigned char *vaddr = phys_to_virt(tlb_addr);
+ unsigned char *vaddr = mem->vaddr + tlb_addr - mem->start;
unsigned int tlb_offset;

if (orig_addr == INVALID_PHYS_ADDR)
--
2.25.1