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    Subject[Patch v4 07/13] swiotlb: Remove bounce buffer remapping for Hyper-V
    Date
    With changes to how Hyper-V guest VMs flip memory between private
    (encrypted) and shared (decrypted), creating a second kernel virtual
    mapping for shared memory is no longer necessary. Everything needed
    for the transition to shared is handled by set_memory_decrypted().

    As such, remove swiotlb_unencrypted_base and the associated
    code.

    Signed-off-by: Michael Kelley <mikelley@microsoft.com>
    Acked-by: Christoph Hellwig <hch@lst.de>
    ---
    arch/x86/kernel/cpu/mshyperv.c | 7 +------
    include/linux/swiotlb.h | 2 --
    kernel/dma/swiotlb.c | 45 +-----------------------------------------
    3 files changed, 2 insertions(+), 52 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
    index b080795..c87e411 100644
    --- a/arch/x86/kernel/cpu/mshyperv.c
    +++ b/arch/x86/kernel/cpu/mshyperv.c
    @@ -18,7 +18,6 @@
    #include <linux/kexec.h>
    #include <linux/i8253.h>
    #include <linux/random.h>
    -#include <linux/swiotlb.h>
    #include <asm/processor.h>
    #include <asm/hypervisor.h>
    #include <asm/hyperv-tlfs.h>
    @@ -332,12 +331,8 @@ static void __init ms_hyperv_init_platform(void)
    pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
    ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);

    - if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
    + if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
    static_branch_enable(&isolation_type_snp);
    -#ifdef CONFIG_SWIOTLB
    - swiotlb_unencrypted_base = ms_hyperv.shared_gpa_boundary;
    -#endif
    - }
    }

    if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
    diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
    index 35bc4e2..13d7075 100644
    --- a/include/linux/swiotlb.h
    +++ b/include/linux/swiotlb.h
    @@ -185,6 +185,4 @@ static inline bool is_swiotlb_for_alloc(struct device *dev)
    }
    #endif /* CONFIG_DMA_RESTRICTED_POOL */

    -extern phys_addr_t swiotlb_unencrypted_base;
    -
    #endif /* __LINUX_SWIOTLB_H */
    diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
    index a34c38b..d3d6be0 100644
    --- a/kernel/dma/swiotlb.c
    +++ b/kernel/dma/swiotlb.c
    @@ -73,8 +73,6 @@ struct io_tlb_slot {

    struct io_tlb_mem io_tlb_default_mem;

    -phys_addr_t swiotlb_unencrypted_base;
    -
    static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
    static unsigned long default_nareas;

    @@ -210,34 +208,6 @@ static inline unsigned long nr_slots(u64 val)
    }

    /*
    - * Remap swioltb memory in the unencrypted physical address space
    - * when swiotlb_unencrypted_base is set. (e.g. for Hyper-V AMD SEV-SNP
    - * Isolation VMs).
    - */
    -#ifdef CONFIG_HAS_IOMEM
    -static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
    -{
    - void *vaddr = NULL;
    -
    - if (swiotlb_unencrypted_base) {
    - phys_addr_t paddr = mem->start + swiotlb_unencrypted_base;
    -
    - vaddr = memremap(paddr, bytes, MEMREMAP_WB);
    - if (!vaddr)
    - pr_err("Failed to map the unencrypted memory %pa size %lx.\n",
    - &paddr, bytes);
    - }
    -
    - return vaddr;
    -}
    -#else
    -static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
    -{
    - return NULL;
    -}
    -#endif
    -
    -/*
    * 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
    @@ -246,18 +216,12 @@ static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
    void __init swiotlb_update_mem_attributes(void)
    {
    struct io_tlb_mem *mem = &io_tlb_default_mem;
    - void *vaddr;
    unsigned long bytes;

    if (!mem->nslabs || mem->late_alloc)
    return;
    - vaddr = phys_to_virt(mem->start);
    bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
    - set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
    -
    - mem->vaddr = swiotlb_mem_remap(mem, bytes);
    - if (!mem->vaddr)
    - mem->vaddr = vaddr;
    + set_memory_decrypted((unsigned long)mem->vaddr, bytes >> PAGE_SHIFT);
    }

    static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
    @@ -288,13 +252,6 @@ static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
    mem->slots[i].alloc_size = 0;
    }

    - /*
    - * If swiotlb_unencrypted_base is set, the bounce buffer memory will
    - * be remapped and cleared in swiotlb_update_mem_attributes.
    - */
    - if (swiotlb_unencrypted_base)
    - return;
    -
    memset(vaddr, 0, bytes);
    mem->vaddr = vaddr;
    return;
    --
    1.8.3.1
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