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    Subject[RFC PATCH v3 13/20] x86: DMA support for memory encryption
    Date
    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 un-encrypted 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 | 17 +++++++++++
    include/linux/swiotlb.h | 1 +
    init/main.c | 13 ++++++++
    lib/swiotlb.c | 58 +++++++++++++++++++++++++++++++-----
    9 files changed, 103 insertions(+), 17 deletions(-)

    diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
    index 4446162..c9cdcae 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)
    @@ -69,12 +70,12 @@ 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 paddr | sme_me_mask;
    }

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

    diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
    index d544481..a024451 100644
    --- a/arch/x86/include/asm/mem_encrypt.h
    +++ b/arch/x86/include/asm/mem_encrypt.h
    @@ -35,6 +35,11 @@ void __init sme_encrypt_ramdisk(resource_size_t paddr,

    void __init sme_early_init(void);

    +/* Architecture __weak replacement functions */
    +void __init mem_encrypt_init(void);
    +
    +void swiotlb_set_mem_unenc(void *vaddr, unsigned long size);
    +
    #define __sme_pa(x) (__pa((x)) | sme_me_mask)
    #define __sme_pa_nodebug(x) (__pa_nodebug((x)) | sme_me_mask)

    diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
    index d30c377..0ce28df 100644
    --- a/arch/x86/kernel/pci-dma.c
    +++ b/arch/x86/kernel/pci-dma.c
    @@ -92,9 +92,12 @@ again:
    /* CMA can be used only in the context which permits sleeping */
    if (gfpflags_allow_blocking(flag)) {
    page = dma_alloc_from_contiguous(dev, count, get_order(size));
    - 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 */
    @@ -103,7 +106,7 @@ again:
    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 00e71ce..922c10d 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 b47edb8..34a9e524 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,
    @@ -64,13 +66,15 @@ static struct dma_map_ops swiotlb_dma_ops = {
    * 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)
    {
    int use_swiotlb = swiotlb | swiotlb_force;

    - if (swiotlb_force)
    + if (swiotlb_force || sme_me_mask)
    swiotlb = 1;

    return use_swiotlb;
    diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
    index 41cfdf9..e351003 100644
    --- a/arch/x86/mm/mem_encrypt.c
    +++ b/arch/x86/mm/mem_encrypt.c
    @@ -13,6 +13,8 @@
    #include <linux/linkage.h>
    #include <linux/init.h>
    #include <linux/mm.h>
    +#include <linux/dma-mapping.h>
    +#include <linux/swiotlb.h>

    #include <asm/tlbflush.h>
    #include <asm/fixmap.h>
    @@ -240,3 +242,18 @@ void __init sme_early_init(void)
    for (i = 0; i < ARRAY_SIZE(protection_map); i++)
    protection_map[i] = __pgprot(pgprot_val(protection_map[i]) | sme_me_mask);
    }
    +
    +/* Architecture __weak replacement functions */
    +void __init mem_encrypt_init(void)
    +{
    + if (!sme_me_mask)
    + return;
    +
    + /* Make SWIOTLB use an unencrypted DMA area */
    + swiotlb_clear_encryption();
    +}
    +
    +void swiotlb_set_mem_unenc(void *vaddr, unsigned long size)
    +{
    + sme_set_mem_unenc(vaddr, size);
    +}
    diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
    index 5f81f8a..5c909fc 100644
    --- a/include/linux/swiotlb.h
    +++ b/include/linux/swiotlb.h
    @@ -29,6 +29,7 @@ int swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose);
    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_clear_encryption(void);

    /*
    * Enumeration for sync targets
    diff --git a/init/main.c b/init/main.c
    index a8a58e2..ae37f0d 100644
    --- a/init/main.c
    +++ b/init/main.c
    @@ -458,6 +458,10 @@ void __init __weak thread_stack_cache_init(void)
    }
    #endif

    +void __init __weak mem_encrypt_init(void)
    +{
    +}
    +
    /*
    * Set up kernel memory allocators
    */
    @@ -598,6 +602,15 @@ 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 un-encrypted 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 22e13a0..638e99c 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>
    @@ -131,6 +132,17 @@ unsigned long swiotlb_size_or_default(void)
    return size ? size : (IO_TLB_DEFAULT_SIZE);
    }

    +void __weak swiotlb_set_mem_unenc(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 phys_to_dma(hwdev, address) & ~sme_me_mask;
    +}
    +
    /* Note that this doesn't work with highmem page */
    static dma_addr_t swiotlb_virt_to_bus(struct device *hwdev,
    volatile void *address)
    @@ -159,6 +171,31 @@ void swiotlb_print_info(void)
    bytes >> 20, vstart, vend - 1);
    }

    +/*
    + * If memory encryption is active, the DMA address for an encrypted page may
    + * be beyond the range of the device. If bounce buffers are required be sure
    + * that they are not on an encrypted page. This should be called before the
    + * iotlb area is used.
    + */
    +void __init swiotlb_clear_encryption(void)
    +{
    + void *vaddr;
    + unsigned long bytes;
    +
    + if (no_iotlb_memory || !io_tlb_start || late_alloc)
    + return;
    +
    + vaddr = phys_to_virt(io_tlb_start);
    + bytes = PAGE_ALIGN(io_tlb_nslabs << IO_TLB_SHIFT);
    + swiotlb_set_mem_unenc(vaddr, bytes);
    + memset(vaddr, 0, bytes);
    +
    + vaddr = phys_to_virt(io_tlb_overflow_buffer);
    + bytes = PAGE_ALIGN(io_tlb_overflow);
    + swiotlb_set_mem_unenc(vaddr, bytes);
    + memset(vaddr, 0, bytes);
    +}
    +
    int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
    {
    void *v_overflow_buffer;
    @@ -294,6 +331,8 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
    io_tlb_start = virt_to_phys(tlb);
    io_tlb_end = io_tlb_start + bytes;

    + /* Keep TLB in unencrypted memory if memory encryption is active */
    + swiotlb_set_mem_unenc(tlb, bytes);
    memset(tlb, 0, bytes);

    /*
    @@ -304,6 +343,9 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
    if (!v_overflow_buffer)
    goto cleanup2;

    + /* Keep overflow in unencrypted memory if memory encryption is active */
    + swiotlb_set_mem_unenc(v_overflow_buffer, io_tlb_overflow);
    + memset(v_overflow_buffer, 0, io_tlb_overflow);
    io_tlb_overflow_buffer = virt_to_phys(v_overflow_buffer);

    /*
    @@ -541,7 +583,7 @@ static phys_addr_t
    map_single(struct device *hwdev, phys_addr_t phys, size_t size,
    enum dma_data_direction dir)
    {
    - dma_addr_t start_dma_addr = phys_to_dma(hwdev, io_tlb_start);
    + dma_addr_t start_dma_addr = swiotlb_phys_to_dma(hwdev, io_tlb_start);

    return swiotlb_tbl_map_single(hwdev, start_dma_addr, phys, size, dir);
    }
    @@ -659,7 +701,7 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
    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) {
    @@ -758,15 +800,15 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
    map = map_single(dev, phys, size, dir);
    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)) {
    swiotlb_tbl_unmap_single(dev, map, size, dir);
    - return phys_to_dma(dev, io_tlb_overflow_buffer);
    + return swiotlb_phys_to_dma(dev, io_tlb_overflow_buffer);
    }

    return dev_addr;
    @@ -901,7 +943,7 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
    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;
    @@ -985,7 +1027,7 @@ EXPORT_SYMBOL(swiotlb_sync_sg_for_device);
    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);

    @@ -998,6 +1040,6 @@ EXPORT_SYMBOL(swiotlb_dma_mapping_error);
    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);
    \
     
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