Re: [RFC PATCH v4 00/28] x86: Secure Memory Encryption (AMD)

Dave Young
2017-03-01T09:17:25Z

Hi Tom,

On 02/16/17 at 09:41am, Tom Lendacky wrote:
> This RFC patch series provides support for AMD's new Secure Memory
> Encryption (SME) feature.
>
> SME can be used to mark individual pages of memory as encrypted through the
> page tables. A page of memory that is marked encrypted will be automatically
> decrypted when read from DRAM and will be automatically encrypted when
> written to DRAM. Details on SME can found in the links below.
>
> The SME feature is identified through a CPUID function and enabled through
> the SYSCFG MSR. Once enabled, page table entries will determine how the
> memory is accessed. If a page table entry has the memory encryption mask set,
> then that memory will be accessed as encrypted memory. The memory encryption
> mask (as well as other related information) is determined from settings
> returned through the same CPUID function that identifies the presence of the
> feature.
>
> The approach that this patch series takes is to encrypt everything possible
> starting early in the boot where the kernel is encrypted. Using the page
> table macros the encryption mask can be incorporated into all page table
> entries and page allocations. By updating the protection map, userspace
> allocations are also marked encrypted. Certain data must be accounted for
> as having been placed in memory before SME was enabled (EFI, initrd, etc.)
> and accessed accordingly.
>
> This patch series is a pre-cursor to another AMD processor feature called
> Secure Encrypted Virtualization (SEV). The support for SEV will build upon
> the SME support and will be submitted later. Details on SEV can be found
> in the links below.
>
> The following links provide additional detail:
>
> AMD Memory Encryption whitepaper:
> http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2013/12/AMD_Memory_Encryption_Whitepaper_v7-Public.pdf
>
> AMD64 Architecture Programmer's Manual:
> http://support.amd.com/TechDocs/24593.pdf
> SME is section 7.10
> SEV is section 15.34
>
> This patch series is based off of the master branch of tip.
> Commit a27cb9e1b2b4 ("Merge branch 'WIP.sched/core'")
>
> ---
>
> Still to do: IOMMU enablement support
>
> Changes since v3:
> - Broke out some of the patches into smaller individual patches
> - Updated Documentation
> - Added a message to indicate why the IOMMU was disabled
> - Updated CPU feature support for SME by taking into account whether
> BIOS has enabled SME
> - Eliminated redundant functions
> - Added some warning messages for DMA usage of bounce buffers when SME
> is active
> - Added support for persistent memory
> - Added support to determine when setup data is being mapped and be sure
> to map it un-encrypted
> - Added CONFIG support to set the default action of whether to activate
> SME if it is supported/enabled
> - Added support for (re)booting with kexec

Could you please add kexec list in cc when you updating the patches so
that kexec/kdump people do not miss them?

>
> Changes since v2:
> - Updated Documentation
> - Make the encryption mask available outside of arch/x86 through a
> standard include file
> - Conversion of assembler routines to C where possible (not everything
> could be converted, e.g. the routine that does the actual encryption
> needs to be copied into a safe location and it is difficult to
> determine the actual length of the function in order to copy it)
> - Fix SME feature use of scattered CPUID feature
> - Creation of SME specific functions for things like encrypting
> the setup data, ramdisk, etc.
> - New take on early_memremap / memremap encryption support
> - Additional support for accessing video buffers (fbdev/gpu) as
> un-encrypted
> - Disable IOMMU for now - need to investigate further in relation to
> how it needs to be programmed relative to accessing physical memory
>
> Changes since v1:
> - Added Documentation.
> - Removed AMD vendor check for setting the PAT write protect mode
> - Updated naming of trampoline flag for SME as well as moving of the
> SME check to before paging is enabled.
> - Change to early_memremap to identify the data being mapped as either
> boot data or kernel data. The idea being that boot data will have
> been placed in memory as un-encrypted data and would need to be accessed
> as such.
> - Updated debugfs support for the bootparams to access the data properly.
> - Do not set the SYSCFG[MEME] bit, only check it. The setting of the
> MemEncryptionModeEn bit results in a reduction of physical address size
> of the processor. It is possible that BIOS could have configured resources
> resources into a range that will now not be addressable. To prevent this,
> rely on BIOS to set the SYSCFG[MEME] bit and only then enable memory
> encryption support in the kernel.
>
> Tom Lendacky (28):
> x86: Documentation for AMD Secure Memory Encryption (SME)
> x86: Set the write-protect cache mode for full PAT support
> x86: Add the Secure Memory Encryption CPU feature
> x86: Handle reduction in physical address size with SME
> x86: Add Secure Memory Encryption (SME) support
> x86: Add support to enable SME during early boot processing
> x86: Provide general kernel support for memory encryption
> x86: Extend the early_memremap support with additional attrs
> x86: Add support for early encryption/decryption of memory
> x86: Insure that boot memory areas are mapped properly
> x86: Add support to determine the E820 type of an address
> efi: Add an EFI table address match function
> efi: Update efi_mem_type() to return defined EFI mem types
> Add support to access boot related data in the clear
> Add support to access persistent memory in the clear
> x86: Add support for changing memory encryption attribute
> x86: Decrypt trampoline area if memory encryption is active
> x86: DMA support for memory encryption
> swiotlb: Add warnings for use of bounce buffers with SME
> iommu/amd: Disable AMD IOMMU if memory encryption is active
> x86: Check for memory encryption on the APs
> x86: Do not specify encrypted memory for video mappings
> x86/kvm: Enable Secure Memory Encryption of nested page tables
> x86: Access the setup data through debugfs decrypted
> x86: Access the setup data through sysfs decrypted
> x86: Allow kexec to be used with SME
> x86: Add support to encrypt the kernel in-place
> x86: Add support to make use of Secure Memory Encryption
>
>
> Documentation/admin-guide/kernel-parameters.txt | 11 +
> Documentation/x86/amd-memory-encryption.txt | 57 ++++
> arch/x86/Kconfig | 26 ++
> arch/x86/boot/compressed/pagetable.c | 7 +
> arch/x86/include/asm/cacheflush.h | 5
> arch/x86/include/asm/cpufeature.h | 7 -
> arch/x86/include/asm/cpufeatures.h | 5
> arch/x86/include/asm/disabled-features.h | 3
> arch/x86/include/asm/dma-mapping.h | 5
> arch/x86/include/asm/e820/api.h | 2
> arch/x86/include/asm/e820/types.h | 2
> arch/x86/include/asm/fixmap.h | 20 +
> arch/x86/include/asm/init.h | 1
> arch/x86/include/asm/io.h | 3
> arch/x86/include/asm/kvm_host.h | 3
> arch/x86/include/asm/mem_encrypt.h | 108 ++++++++
> arch/x86/include/asm/msr-index.h | 2
> arch/x86/include/asm/page.h | 4
> arch/x86/include/asm/pgtable.h | 26 +-
> arch/x86/include/asm/pgtable_types.h | 54 +++-
> arch/x86/include/asm/processor.h | 3
> arch/x86/include/asm/realmode.h | 12 +
> arch/x86/include/asm/required-features.h | 3
> arch/x86/include/asm/setup.h | 8 +
> arch/x86/include/asm/vga.h | 13 +
> arch/x86/kernel/Makefile | 3
> arch/x86/kernel/cpu/common.c | 23 ++
> arch/x86/kernel/e820.c | 26 ++
> arch/x86/kernel/espfix_64.c | 2
> arch/x86/kernel/head64.c | 46 +++
> arch/x86/kernel/head_64.S | 65 ++++-
> arch/x86/kernel/kdebugfs.c | 30 +-
> arch/x86/kernel/ksysfs.c | 27 +-
> arch/x86/kernel/machine_kexec_64.c | 3
> arch/x86/kernel/mem_encrypt_boot.S | 156 ++++++++++++
> arch/x86/kernel/mem_encrypt_init.c | 310 +++++++++++++++++++++++
> arch/x86/kernel/pci-dma.c | 11 +
> arch/x86/kernel/pci-nommu.c | 2
> arch/x86/kernel/pci-swiotlb.c | 8 -
> arch/x86/kernel/process.c | 43 +++
> arch/x86/kernel/setup.c | 43 +++
> arch/x86/kernel/smp.c | 4
> arch/x86/kvm/mmu.c | 8 -
> arch/x86/kvm/vmx.c | 3
> arch/x86/kvm/x86.c | 3
> arch/x86/mm/Makefile | 1
> arch/x86/mm/ident_map.c | 6
> arch/x86/mm/ioremap.c | 157 ++++++++++++
> arch/x86/mm/kasan_init_64.c | 4
> arch/x86/mm/mem_encrypt.c | 218 ++++++++++++++++
> arch/x86/mm/pageattr.c | 71 +++++
> arch/x86/mm/pat.c | 6
> arch/x86/platform/efi/efi.c | 4
> arch/x86/platform/efi/efi_64.c | 16 +
> arch/x86/realmode/init.c | 16 +
> arch/x86/realmode/rm/trampoline_64.S | 17 +
> drivers/firmware/efi/efi.c | 33 ++
> drivers/gpu/drm/drm_gem.c | 2
> drivers/gpu/drm/drm_vm.c | 4
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 7 -
> drivers/gpu/drm/udl/udl_fb.c | 4
> drivers/iommu/amd_iommu_init.c | 7 +
> drivers/video/fbdev/core/fbmem.c | 12 +
> include/asm-generic/early_ioremap.h | 2
> include/asm-generic/pgtable.h | 8 +
> include/linux/dma-mapping.h | 11 +
> include/linux/efi.h | 7 +
> include/linux/mem_encrypt.h | 53 ++++
> include/linux/swiotlb.h | 1
> init/main.c | 13 +
> kernel/kexec_core.c | 24 ++
> kernel/memremap.c | 11 +
> lib/swiotlb.c | 59 ++++
> mm/early_ioremap.c | 28 ++
> 74 files changed, 1880 insertions(+), 128 deletions(-)
> create mode 100644 Documentation/x86/amd-memory-encryption.txt
> create mode 100644 arch/x86/include/asm/mem_encrypt.h
> create mode 100644 arch/x86/kernel/mem_encrypt_boot.S
> create mode 100644 arch/x86/kernel/mem_encrypt_init.c
> create mode 100644 arch/x86/mm/mem_encrypt.c
> create mode 100644 include/linux/mem_encrypt.h
>
> --
> Tom Lendacky
> --
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Thanks a lot!
Dave

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