Re: [Resend RFC PATCH V4 09/13] x86/Swiotlb/HV: Add Swiotlb bounce buffer remap function for HV IVM

[Tianyu Lan <ltykernel@gmail.com>]

Hi Christoph & Konrad:
     Could you review this patch and make sure this is right way to 
resolve the memory remap request from AMD SEV-SNP vTOM case?

Thanks.

On 7/7/2021 11:46 PM, 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.
> 
> Introduce set_memory_decrypted_map() function to decrypt memory and
> remap memory with platform callback. Use set_memory_decrypted_
> map() in the swiotlb code, store remap address returned by the new
> API and use the remap address to copy data from/to swiotlb bounce buffer.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
>   arch/x86/hyperv/ivm.c             | 30 ++++++++++++++++++++++++++++++
>   arch/x86/include/asm/mshyperv.h   |  2 ++
>   arch/x86/include/asm/set_memory.h |  2 ++
>   arch/x86/mm/pat/set_memory.c      | 28 ++++++++++++++++++++++++++++
>   include/linux/swiotlb.h           |  4 ++++
>   kernel/dma/swiotlb.c              | 11 ++++++++---
>   6 files changed, 74 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
> index 8a6f4e9e3d6c..ea33935e0c17 100644
> --- a/arch/x86/hyperv/ivm.c
> +++ b/arch/x86/hyperv/ivm.c
> @@ -267,3 +267,33 @@ int hv_set_mem_enc(unsigned long addr, int numpages, bool enc)
>   			enc ? VMBUS_PAGE_NOT_VISIBLE
>   			: VMBUS_PAGE_VISIBLE_READ_WRITE);
>   }
> +
> +/*
> + * hv_map_memory - map memory to extra space in the AMD SEV-SNP Isolation VM.
> + */
> +unsigned long hv_map_memory(unsigned long addr, unsigned long size)
> +{
> +	unsigned long *pfns = kcalloc(size / HV_HYP_PAGE_SIZE,
> +				      sizeof(unsigned long),
> +		       GFP_KERNEL);
> +	unsigned long vaddr;
> +	int i;
> +
> +	if (!pfns)
> +		return (unsigned long)NULL;
> +
> +	for (i = 0; i < size / HV_HYP_PAGE_SIZE; i++)
> +		pfns[i] = virt_to_hvpfn((void *)addr + i * HV_HYP_PAGE_SIZE) +
> +			(ms_hyperv.shared_gpa_boundary >> HV_HYP_PAGE_SHIFT);
> +
> +	vaddr = (unsigned long)vmap_pfn(pfns, size / HV_HYP_PAGE_SIZE,
> +					PAGE_KERNEL_IO);
> +	kfree(pfns);
> +
> +	return vaddr;
> +}
> +
> +void hv_unmap_memory(unsigned long addr)
> +{
> +	vunmap((void *)addr);
> +}
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index fe03e3e833ac..ba3cb9e32fdb 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -253,6 +253,8 @@ int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector,
>   int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry);
>   int hv_mark_gpa_visibility(u16 count, const u64 pfn[], u32 visibility);
>   int hv_set_mem_enc(unsigned long addr, int numpages, bool enc);
> +unsigned long hv_map_memory(unsigned long addr, unsigned long size);
> +void hv_unmap_memory(unsigned long addr);
>   void hv_sint_wrmsrl_ghcb(u64 msr, u64 value);
>   void hv_sint_rdmsrl_ghcb(u64 msr, u64 *value);
>   void hv_signal_eom_ghcb(void);
> diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
> index 43fa081a1adb..7a2117931830 100644
> --- a/arch/x86/include/asm/set_memory.h
> +++ b/arch/x86/include/asm/set_memory.h
> @@ -49,6 +49,8 @@ int set_memory_decrypted(unsigned long addr, int numpages);
>   int set_memory_np_noalias(unsigned long addr, int numpages);
>   int set_memory_nonglobal(unsigned long addr, int numpages);
>   int set_memory_global(unsigned long addr, int numpages);
> +unsigned long set_memory_decrypted_map(unsigned long addr, unsigned long size);
> +int set_memory_encrypted_unmap(unsigned long addr, unsigned long size);
>   
>   int set_pages_array_uc(struct page **pages, int addrinarray);
>   int set_pages_array_wc(struct page **pages, int addrinarray);
> diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
> index 6cc83c57383d..5d4d3963f4a2 100644
> --- a/arch/x86/mm/pat/set_memory.c
> +++ b/arch/x86/mm/pat/set_memory.c
> @@ -2039,6 +2039,34 @@ int set_memory_decrypted(unsigned long addr, int numpages)
>   }
>   EXPORT_SYMBOL_GPL(set_memory_decrypted);
>   
> +static unsigned long __map_memory(unsigned long addr, unsigned long size)
> +{
> +	if (hv_is_isolation_supported())
> +		return hv_map_memory(addr, size);
> +
> +	return addr;
> +}
> +
> +static void __unmap_memory(unsigned long addr)
> +{
> +	if (hv_is_isolation_supported())
> +		hv_unmap_memory(addr);
> +}
> +
> +unsigned long set_memory_decrypted_map(unsigned long addr, unsigned long size)
> +{
> +	if (__set_memory_enc_dec(addr, size / PAGE_SIZE, false))
> +		return (unsigned long)NULL;
> +
> +	return __map_memory(addr, size);
> +}
> +
> +int set_memory_encrypted_unmap(unsigned long addr, unsigned long size)
> +{
> +	__unmap_memory(addr);
> +	return __set_memory_enc_dec(addr, size / PAGE_SIZE, true);
> +}
> +
>   int set_pages_uc(struct page *page, int numpages)
>   {
>   	unsigned long addr = (unsigned long)page_address(page);
> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
> index f507e3eacbea..5c6f6c7380ef 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.
> + * @vstart:	The virtual start address 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 *vstart;
>   	unsigned long nslabs;
>   	unsigned long used;
>   	unsigned int index;
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index d3fa4669229b..9911817250a8 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -194,8 +194,13 @@ 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->vstart = (void *)set_memory_decrypted_map((unsigned long)vaddr, bytes);
> +	if (!mem->vstart) {
> +		pr_err("Failed to decrypt memory.\n");
> +		return;
> +	}
> +
> +	memset(mem->vstart, 0, bytes);
>   }
>   
>   int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
> @@ -352,7 +357,7 @@ 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->vstart + tlb_addr - mem->start;
>   
>   	if (orig_addr == INVALID_PHYS_ADDR)
>   		return;
>