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    Subject[PATCH v1 1/7] x86/mm: Move force_dma_unencrypted() to common code
    Date
    From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

    Intel TDX doesn't allow VMM to access guest private memory.
    Any memory that is required for communication with VMM must
    be shared explicitly by setting the bit in page table entry.
    After setting the shared bit, the conversion must be completed
    with MapGPA hypercall. You can find details about MapGPA
    hypercall in [1], sec 3.2.

    The call informs VMM about the conversion between
    private/shared mappings. The shared memory is similar to
    unencrypted memory in AMD SME/SEV terminology but the
    underlying process of sharing/un-sharing the memory is
    different for Intel TDX guest platform.

    SEV assumes that I/O devices can only do DMA to "decrypted"
    physical addresses without the C-bit set. In order for the CPU
    to interact with this memory, the CPU needs a decrypted mapping.
    To add this support, AMD SME code forces force_dma_unencrypted()
    to return true for platforms that support AMD SEV feature. It
    will be used for DMA memory allocation API to trigger
    set_memory_decrypted() for platforms that support AMD SEV
    feature.

    TDX is similar. So, to communicate with I/O devices, related
    pages need to be marked as shared. As mentioned above, shared
    memory in TDX architecture is similar to decrypted memory in
    AMD SME/SEV. So similar to AMD SEV, force_dma_unencrypted() has
    to forced to return true. This support is added in other patches
    in this series.

    So move force_dma_unencrypted() out of AMD specific code and call
    AMD specific (amd_force_dma_unencrypted()) initialization function
    from it. force_dma_unencrypted() will be modified by later patches
    to include Intel TDX guest platform specific initialization.

    Also, introduce new config option X86_MEM_ENCRYPT_COMMON that has
    to be selected by all x86 memory encryption features. This will be
    selected by both AMD SEV and Intel TDX guest config options.

    This is preparation for TDX changes in DMA code and it has no
    functional change.

    [1] - https://software.intel.com/content/dam/develop/external/us/en/documents/intel-tdx-guest-hypervisor-communication-interface.pdf

    Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Reviewed-by: Andi Kleen <ak@linux.intel.com>
    Reviewed-by: Tony Luck <tony.luck@intel.com>
    Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
    ---
    arch/x86/Kconfig | 8 ++++++--
    arch/x86/include/asm/mem_encrypt_common.h | 18 ++++++++++++++++++
    arch/x86/mm/Makefile | 2 ++
    arch/x86/mm/mem_encrypt.c | 5 +++--
    arch/x86/mm/mem_encrypt_common.c | 20 ++++++++++++++++++++
    5 files changed, 49 insertions(+), 4 deletions(-)
    create mode 100644 arch/x86/include/asm/mem_encrypt_common.h
    create mode 100644 arch/x86/mm/mem_encrypt_common.c

    diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    index fc51579e54ad..2adc0df1838b 100644
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -1536,16 +1536,20 @@ config X86_CPA_STATISTICS
    helps to determine the effectiveness of preserving large and huge
    page mappings when mapping protections are changed.

    +config X86_MEM_ENCRYPT_COMMON
    + select ARCH_HAS_FORCE_DMA_UNENCRYPTED
    + select DYNAMIC_PHYSICAL_MASK
    + def_bool n
    +
    config AMD_MEM_ENCRYPT
    bool "AMD Secure Memory Encryption (SME) support"
    depends on X86_64 && CPU_SUP_AMD
    select DMA_COHERENT_POOL
    - select DYNAMIC_PHYSICAL_MASK
    select ARCH_USE_MEMREMAP_PROT
    - select ARCH_HAS_FORCE_DMA_UNENCRYPTED
    select INSTRUCTION_DECODER
    select ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS
    select ARCH_HAS_PROTECTED_GUEST
    + select X86_MEM_ENCRYPT_COMMON
    help
    Say yes to enable support for the encryption of system memory.
    This requires an AMD processor that supports Secure Memory
    diff --git a/arch/x86/include/asm/mem_encrypt_common.h b/arch/x86/include/asm/mem_encrypt_common.h
    new file mode 100644
    index 000000000000..697bc40a4e3d
    --- /dev/null
    +++ b/arch/x86/include/asm/mem_encrypt_common.h
    @@ -0,0 +1,18 @@
    +/* SPDX-License-Identifier: GPL-2.0 */
    +/* Copyright (C) 2020 Intel Corporation */
    +#ifndef _ASM_X86_MEM_ENCRYPT_COMMON_H
    +#define _ASM_X86_MEM_ENCRYPT_COMMON_H
    +
    +#include <linux/mem_encrypt.h>
    +#include <linux/device.h>
    +
    +#ifdef CONFIG_AMD_MEM_ENCRYPT
    +bool amd_force_dma_unencrypted(struct device *dev);
    +#else /* CONFIG_AMD_MEM_ENCRYPT */
    +static inline bool amd_force_dma_unencrypted(struct device *dev)
    +{
    + return false;
    +}
    +#endif /* CONFIG_AMD_MEM_ENCRYPT */
    +
    +#endif
    diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
    index 5864219221ca..b31cb52bf1bd 100644
    --- a/arch/x86/mm/Makefile
    +++ b/arch/x86/mm/Makefile
    @@ -52,6 +52,8 @@ obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) += pkeys.o
    obj-$(CONFIG_RANDOMIZE_MEMORY) += kaslr.o
    obj-$(CONFIG_PAGE_TABLE_ISOLATION) += pti.o

    +obj-$(CONFIG_X86_MEM_ENCRYPT_COMMON) += mem_encrypt_common.o
    +
    obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt.o
    obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt_identity.o
    obj-$(CONFIG_AMD_MEM_ENCRYPT) += mem_encrypt_boot.o
    diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
    index d0026bce47df..9c55a3209c88 100644
    --- a/arch/x86/mm/mem_encrypt.c
    +++ b/arch/x86/mm/mem_encrypt.c
    @@ -31,6 +31,7 @@
    #include <asm/processor-flags.h>
    #include <asm/msr.h>
    #include <asm/cmdline.h>
    +#include <asm/mem_encrypt_common.h>

    #include "mm_internal.h"

    @@ -390,8 +391,8 @@ bool noinstr sev_es_active(void)
    return sev_status & MSR_AMD64_SEV_ES_ENABLED;
    }

    -/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
    -bool force_dma_unencrypted(struct device *dev)
    +/* Override for DMA direct allocation check - AMD specific initialization */
    +bool amd_force_dma_unencrypted(struct device *dev)
    {
    /*
    * For SEV, all DMA must be to unencrypted addresses.
    diff --git a/arch/x86/mm/mem_encrypt_common.c b/arch/x86/mm/mem_encrypt_common.c
    new file mode 100644
    index 000000000000..4a9a4d5f36cd
    --- /dev/null
    +++ b/arch/x86/mm/mem_encrypt_common.c
    @@ -0,0 +1,20 @@
    +// SPDX-License-Identifier: GPL-2.0-only
    +/*
    + * Memory Encryption Support Common Code
    + *
    + * Copyright (C) 2021 Intel Corporation
    + *
    + * Author: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
    + */
    +
    +#include <asm/mem_encrypt_common.h>
    +#include <linux/dma-mapping.h>
    +
    +/* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
    +bool force_dma_unencrypted(struct device *dev)
    +{
    + if (sev_active() || sme_active())
    + return amd_force_dma_unencrypted(dev);
    +
    + return false;
    +}
    --
    2.25.1
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