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diff --git a/Documentation/virtual/kvm/amd-memory-encryption.rst b/Documentation/virtual/kvm/amd-memory-encryption.rst new file mode 100644 index 000000000000..a8ef21e737db --- /dev/null +++ b/Documentation/virtual/kvm/amd-memory-encryption.rst @@ -0,0 +1,45 @@ +====================================== +Secure Encrypted Virtualization (SEV) +====================================== + +Overview +======== + +Secure Encrypted Virtualization (SEV) is a feature found on AMD processors. + +SEV is an extension to the AMD-V architecture which supports running +virtual machines (VMs) under the control of a hypervisor. When enabled, +the memory contents of a VM will be transparently encrypted with a key +unique to that VM. + +The hypervisor can determine the SEV support through the CPUID +instruction. The CPUID function 0x8000001f reports information related +to SEV:: + + 0x8000001f[eax]: + Bit[1] indicates support for SEV + ... + [ecx]: + Bits[31:0] Number of encrypted guests supported simultaneously + +If support for SEV is present, MSR 0xc001_0010 (MSR_K8_SYSCFG) and MSR 0xc001_0015 +(MSR_K7_HWCR) can be used to determine if it can be enabled:: + + 0xc001_0010: + Bit[23] 1 = memory encryption can be enabled + 0 = memory encryption can not be enabled + + 0xc001_0015: + Bit[0] 1 = memory encryption can be enabled + 0 = memory encryption can not be enabled + +When SEV support is available, it can be enabled in a specific VM by +setting the SEV bit before executing VMRUN.:: + + VMCB[0x90]: + Bit[1] 1 = SEV is enabled + 0 = SEV is disabled + +SEV hardware uses ASIDs to associate a memory encryption key with a VM. +Hence, the ASID for the SEV-enabled guests must be from 1 to a maximum value +defined in the CPUID 0x8000001f[ecx] field. |