On 09/02/2016 03:50 AM, Borislav Petkov wrote: > On Mon, Aug 22, 2016 at 05:35:39PM -0500, Tom Lendacky wrote: >> This patch adds a Documenation entry to decribe the AMD Secure Memory >> Encryption (SME) feature. >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx> >> --- >> Documentation/x86/amd-memory-encryption.txt | 35 +++++++++++++++++++++++++++ >> 1 file changed, 35 insertions(+) >> create mode 100644 Documentation/x86/amd-memory-encryption.txt >> >> diff --git a/Documentation/x86/amd-memory-encryption.txt b/Documentation/x86/amd-memory-encryption.txt >> new file mode 100644 >> index 0000000..f19c555 >> --- /dev/null >> +++ b/Documentation/x86/amd-memory-encryption.txt >> @@ -0,0 +1,35 @@ >> +Secure Memory Encryption (SME) is a feature found on AMD processors. >> + >> +SME provides the ability to mark individual pages of memory as encrypted using >> +the standard x86 page tables. A page that is marked encrpyted will be > > s/encrpyted/encrypted/ Ugh.. I thought I caught all of these. Obviously not. I'll go through all the patches on this. > >> +automatically decrypted when read from DRAM and encrypted when written to >> +DRAM. SME can therefore be used to protect the contents of DRAM from physical >> +attacks on the system. >> + >> +Support for SME can be determined through the CPUID instruction. The CPUID >> +function 0x8000001f reports information related to SME: >> + >> + 0x8000001f[eax]: >> + Bit[0] indicates support for SME >> + 0x8000001f[ebx]: >> + Bit[5:0] pagetable bit number used to enable memory encryption >> + Bit[11:6] reduction in physical address space, in bits, when >> + memory encryption is enabled (this only affects system >> + physical addresses, not guest physical addresses) >> + >> +If support for SME is present, MSR 0xc00100010 (SYS_CFG) can be used to >> +determine if SME is enabled and/or to enable memory encryption: >> + >> + 0xc0010010: >> + Bit[23] 0 = memory encryption features are disabled >> + 1 = memory encryption features are enabled >> + >> +Linux relies on BIOS to set this bit if BIOS has determined that the reduction >> +in the physical address space as a result of enabling memory encryption (see >> +CPUID information above) will not conflict with the address space resource >> +requirements for the system. If this bit is not set upon Linux startup then >> +Linux itself will not set it and memory encryption will not be possible. >> + >> +SME support is configurable in the kernel through the AMD_MEM_ENCRYPT config >> +option. > > " ... is configurable through CONFIG_AMD_MEM_ENCRYPT." Ok. > >> Additionally, the mem_encrypt=on command line parameter is required >> +to activate memory encryption. > > I think you want to rewrite the logic here to say that people should use > the BIOS option and if none is present for whatever reason, resort to > the alternative "mem_encrypt=on" kernel command line option, no? Yes, I'll work on rewording this section. Thanks, Tom > -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
