Documentation/virtual/kvm: Add AMD Secure Encrypted Virtualization (SEV)

Create a Documentation entry to describe the AMD Secure Encrypted
Virtualization (SEV) feature.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: kvm@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>

diff --git a/Documentation/virtual/kvm/00-INDEX b/Documentation/virtual/kvm/00-INDEX
index 69fe1a8b7ad16ed34311a4676dfc8858ae3532d1..3da73aabff5ac0b126dce945e0e13f77289ccb1b 100644 (file)
--- a/Documentation/virtual/kvm/00-INDEX
+++ b/Documentation/virtual/kvm/00-INDEX
@@ -26,3 +26,6 @@ s390-diag.txt
        - Diagnose hypercall description (for IBM S/390)
 timekeeping.txt
        - timekeeping virtualization for x86-based architectures.
+amd-memory-encryption.txt
+       - notes on AMD Secure Encrypted Virtualization feature and SEV firmware
+         command description

diff --git a/Documentation/virtual/kvm/amd-memory-encryption.rst b/Documentation/virtual/kvm/amd-memory-encryption.rst
new file mode 100644 (file)
index 0000000..a8ef21e
--- /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.