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    Subject[PATCHv5 00/19] MKTME enabling
    Date
    Multikey Total Memory Encryption (MKTME)[1] is a technology that allows
    transparent memory encryption in upcoming Intel platforms. See overview
    below.

    Here's updated version of my patchset that brings support of MKTME.
    Please review and consider applying.

    The patchset provides in-kernel infrastructure for MKTME, but doesn't yet
    have userspace interface.

    First 8 patches are for core-mm. The rest is x86-specific.

    The patchset is on top of tip- tree plus page_ext cleanups I've posted
    earlier[2]. page_ext cleanups are in -mm tree now.

    Below is performance numbers for kernel build. Enabling MKTME doesn't
    affect performance of non-encrypted memory allocation.

    For encrypted memory allocation requires cache flush on allocation and
    freeing encrypted memory. For kernel build it results in ~20% performance
    degradation if we allocate all anonymous memory as encrypted.

    We would need to maintain per-KeyID pool of free pages to minimize cache
    flushing. I'm going to work on the optimization on top of this patchset.

    The patchset also can be found here:

    git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git mktme/wip

    v5:
    - Do not merge VMAs with different KeyID (for real).

    - Do not use zero page in encrypted VMAs.

    - Avoid division in __pa(). The division is replaced with masking which
    makes it near-free. I was not able to measure difference comparing to
    base line. direct_mapping_size now has to be power-of-2 if MKTME
    enabled. Only in this case we can use masking there.

    v4:
    - Address Dave's feedback.

    - Add performance numbers.

    v3:
    - Kernel now can access encrypted pages via per-KeyID direct mapping.

    - Rework page allocation for encrypted memory to minimize overhead on
    non-encrypted pages. It comes with cost for allocation of encrypted
    pages: we have to flush cache on every time we allocate *and* free
    encrypted page. We will need to optimize it later.

    v2:
    - Store KeyID of page in page_ext->flags rather than in anon_vma.
    anon_vma approach turned out to be problematic. The main problem is
    that anon_vma of the page is no longer stable after last mapcount has
    gone. We would like to preserve last used KeyID even for freed
    pages as it allows to avoid unnecessary cache flushing on allocation
    of an encrypted page. page_ext serves this well enough.

    - KeyID is now propagated through page allocator. No need in GFP_ENCRYPT
    anymore.

    - Patch "Decouple dynamic __PHYSICAL_MASK from AMD SME" has been fix to
    work with AMD SEV (need to be confirmed by AMD folks).

    ------------------------------------------------------------------------------

    MKTME is built on top of TME. TME allows encryption of the entirety of
    system memory using a single key. MKTME allows to have multiple encryption
    domains, each having own key -- different memory pages can be encrypted
    with different keys.

    Key design points of Intel MKTME:

    - Initial HW implementation would support upto 63 keys (plus one default
    TME key). But the number of keys may be as low as 3, depending to SKU
    and BIOS settings

    - To access encrypted memory you need to use mapping with proper KeyID
    int the page table entry. KeyID is encoded in upper bits of PFN in page
    table entry.

    - CPU does not enforce coherency between mappings of the same physical
    page with different KeyIDs or encryption keys. We wound need to take
    care about flushing cache on allocation of encrypted page and on
    returning it back to free pool.

    - For managing keys, there's MKTME_KEY_PROGRAM leaf of the new PCONFIG
    (platform configuration) instruction. It allows load and clear keys
    associated with a KeyID. You can also ask CPU to generate a key for
    you or disable memory encryption when a KeyID is used.

    Performance numbers for kernel build:

    Base (tip- tree):

    Performance counter stats for 'sh -c make -j100 -B -k >/dev/null' (5 runs):

    5664711.936917 task-clock (msec) # 34.815 CPUs utilized ( +- 0.02% )
    1,033,886 context-switches # 0.183 K/sec ( +- 0.37% )
    189,308 cpu-migrations # 0.033 K/sec ( +- 0.39% )
    104,951,554 page-faults # 0.019 M/sec ( +- 0.01% )
    16,907,670,543,945 cycles # 2.985 GHz ( +- 0.01% )
    12,662,345,427,578 stalled-cycles-frontend # 74.89% frontend cycles idle ( +- 0.02% )
    9,936,469,878,830 instructions # 0.59 insn per cycle
    # 1.27 stalled cycles per insn ( +- 0.00% )
    2,179,100,082,611 branches # 384.680 M/sec ( +- 0.00% )
    91,235,200,652 branch-misses # 4.19% of all branches ( +- 0.01% )

    162.706797586 seconds time elapsed ( +- 0.04% )

    CONFIG_X86_INTEL_MKTME=y, no encrypted memory:

    Performance counter stats for 'sh -c make -j100 -B -k >/dev/null' (5 runs):

    5668508.245004 task-clock (msec) # 34.872 CPUs utilized ( +- 0.02% )
    1,032,034 context-switches # 0.182 K/sec ( +- 0.90% )
    188,098 cpu-migrations # 0.033 K/sec ( +- 1.15% )
    104,964,084 page-faults # 0.019 M/sec ( +- 0.01% )
    16,919,270,913,026 cycles # 2.985 GHz ( +- 0.02% )
    12,672,067,815,805 stalled-cycles-frontend # 74.90% frontend cycles idle ( +- 0.02% )
    9,942,560,135,477 instructions # 0.59 insn per cycle
    # 1.27 stalled cycles per insn ( +- 0.00% )
    2,180,800,745,687 branches # 384.722 M/sec ( +- 0.00% )
    91,167,857,700 branch-misses # 4.18% of all branches ( +- 0.02% )

    162.552503629 seconds time elapsed ( +- 0.10% )

    CONFIG_X86_INTEL_MKTME=y, all anonymous memory encrypted with KeyID-1, pay
    cache flush overhead on allocation and free:

    Performance counter stats for 'sh -c make -j100 -B -k >/dev/null' (5 runs):

    7041851.999259 task-clock (msec) # 35.915 CPUs utilized ( +- 0.01% )
    1,118,938 context-switches # 0.159 K/sec ( +- 0.49% )
    197,039 cpu-migrations # 0.028 K/sec ( +- 0.80% )
    104,970,021 page-faults # 0.015 M/sec ( +- 0.00% )
    21,025,639,251,627 cycles # 2.986 GHz ( +- 0.01% )
    16,729,451,765,492 stalled-cycles-frontend # 79.57% frontend cycles idle ( +- 0.02% )
    10,010,727,735,588 instructions # 0.48 insn per cycle
    # 1.67 stalled cycles per insn ( +- 0.00% )
    2,197,110,181,421 branches # 312.007 M/sec ( +- 0.00% )
    91,119,463,513 branch-misses # 4.15% of all branches ( +- 0.01% )

    196.072361087 seconds time elapsed ( +- 0.14% )

    [1] https://software.intel.com/sites/default/files/managed/a5/16/Multi-Key-Total-Memory-Encryption-Spec.pdf
    [2] https://lkml.kernel.org/r/20180531135457.20167-1-kirill.shutemov@linux.intel.com

    Kirill A. Shutemov (19):
    mm: Do no merge VMAs with different encryption KeyIDs
    mm: Do not use zero page in encrypted pages
    mm/ksm: Do not merge pages with different KeyIDs
    mm/page_alloc: Unify alloc_hugepage_vma()
    mm/page_alloc: Handle allocation for encrypted memory
    mm/khugepaged: Handle encrypted pages
    x86/mm: Mask out KeyID bits from page table entry pfn
    x86/mm: Introduce variables to store number, shift and mask of KeyIDs
    x86/mm: Preserve KeyID on pte_modify() and pgprot_modify()
    x86/mm: Implement page_keyid() using page_ext
    x86/mm: Implement vma_keyid()
    x86/mm: Implement prep_encrypted_page() and arch_free_page()
    x86/mm: Rename CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING
    x86/mm: Allow to disable MKTME after enumeration
    x86/mm: Detect MKTME early
    x86/mm: Calculate direct mapping size
    x86/mm: Implement sync_direct_mapping()
    x86/mm: Handle encrypted memory in page_to_virt() and __pa()
    x86: Introduce CONFIG_X86_INTEL_MKTME

    Documentation/x86/x86_64/mm.txt | 4 +
    arch/alpha/include/asm/page.h | 2 +-
    arch/s390/include/asm/pgtable.h | 2 +-
    arch/x86/Kconfig | 21 +-
    arch/x86/include/asm/mktme.h | 47 +++
    arch/x86/include/asm/page.h | 1 +
    arch/x86/include/asm/page_64.h | 4 +-
    arch/x86/include/asm/pgtable_types.h | 15 +-
    arch/x86/include/asm/setup.h | 6 +
    arch/x86/kernel/cpu/intel.c | 32 +-
    arch/x86/kernel/head64.c | 4 +
    arch/x86/kernel/setup.c | 3 +
    arch/x86/mm/Makefile | 2 +
    arch/x86/mm/init_64.c | 68 ++++
    arch/x86/mm/kaslr.c | 11 +-
    arch/x86/mm/mktme.c | 546 +++++++++++++++++++++++++++
    fs/userfaultfd.c | 7 +-
    include/linux/gfp.h | 54 ++-
    include/linux/migrate.h | 12 +-
    include/linux/mm.h | 20 +-
    include/linux/page_ext.h | 11 +-
    mm/compaction.c | 1 +
    mm/huge_memory.c | 3 +-
    mm/khugepaged.c | 10 +
    mm/ksm.c | 3 +
    mm/madvise.c | 2 +-
    mm/memory.c | 3 +-
    mm/mempolicy.c | 31 +-
    mm/migrate.c | 4 +-
    mm/mlock.c | 2 +-
    mm/mmap.c | 31 +-
    mm/mprotect.c | 2 +-
    mm/page_alloc.c | 47 +++
    mm/page_ext.c | 3 +
    34 files changed, 954 insertions(+), 60 deletions(-)
    create mode 100644 arch/x86/include/asm/mktme.h
    create mode 100644 arch/x86/mm/mktme.c

    --
    2.18.0

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