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

[Tianyu Lan <ltykernel@gmail.com>]

Hi Konrad:
      Could you have a look at this new version? The change since v1 is 
make swiotlb_init_io_tlb_mem() return error code when 
dma_map_decrypted() fails according your previous comment. If this 
change is ok, could you give your ack and this series needs to be merged 
via Hyper-V next tree.

Thanks.

On 8/5/2021 2:45 AM, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@microsoft.com>
> 
> 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)
>