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

Tom Lendacky
2017-02-16T15:42:08Z

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

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