[Part2 PATCH v4 01/29] Documentation/virtual/kvm: Add AMD Secure Encrypted Virtualization (SEV)

[Brijesh Singh]

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

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: "Radim KrÄmÃÅ" <rkrcmar@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
 Documentation/virtual/kvm/00-INDEX                 |   3 +
 .../virtual/kvm/amd-memory-encryption.txt          | 210 +++++++++++++++++++++
 2 files changed, 213 insertions(+)
 create mode 100644 Documentation/virtual/kvm/amd-memory-encryption.txt

diff --git a/Documentation/virtual/kvm/00-INDEX b/Documentation/virtual/kvm/00-INDEX
index 69fe1a8b7ad1..3da73aabff5a 100644
--- 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.txt b/Documentation/virtual/kvm/amd-memory-encryption.txt
new file mode 100644
index 000000000000..5586d51a8983
--- /dev/null
+++ b/Documentation/virtual/kvm/amd-memory-encryption.txt
@@ -0,0 +1,210 @@
+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 VM will be transparently encrypted with a key unique to the VM.
+
+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 guest supported simultaneously
+
+If support for SEV is present, MSR 0xc001_0010 (MSR_K8_SYSCFG) and MSR
+0xc001_0015 (MSR_K7_HWCR_SMMLOCK) can be used to determine if it can be enabled:
+
+	0xc001_0010:
+		Bit[23]	   0 = memory encryption can be enabled
+			   0 = memory encryption can not be enabled
+
+	0xc001_0015:
+		Bit[0]	   0 = memory encryption can not be enabled
+			   1 = memory encryption can be enabled
+
+When SEV support is available, it can be enabled in specific VM during the VMRUN
+instruction by setting SEV bit in VMCB offset 090h:
+
+	VMCB[0x90]:
+		Bit[1]	    1 = Enable SEV
+
+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 function 0x8000001f[ecx] field.
+
+SEV Key Management
+------------------
+The Key management for the SEV guest is handled by a separate processor known as
+the AMD Secure Processor (AMD-SP). Firmware running inside the AMD-SP provides a
+secure key management interface to perform common hypervisor activities such as
+encrypting bootstrap code, snapshot, migrating and debugging the guest. For
+more information, see SEV Key Management spec at
+
+http://support.amd.com/TechDocs/55766_SEV-KM%20API_Specification.pdf
+
+KVM implements the following commands to support SEV guests launch, migrate
+and save/restore.
+
+1. KVM_SEV_LAUNCH_START
+
+Parameters: struct  kvm_sev_launch_start (in/out)
+Returns: 0 on success, -negative on error
+
+The KVM_SEV_LAUNCH_START command is used for creation the encryption context.
+To create the encryption context, user must provide a guest policy, the owner's
+public Diffie-Hellman (PDH) key and session information.
+
+struct kvm_sev_launch_start {
+	/* if zero then FW creates a new handle */
+	__u32 handle;
+
+	/* guest policy */
+	__u32 policy;
+
+	/* userspace address pointing to the guest owner's PDH key */
+	__u64 dh_uaddr;
+	__u32 dh_len;
+
+	/* userspace address which points to the guest session information */
+	__u64 session_addr;
+	__u32 session_len;
+};
+
+On success, the 'handle' field contain a new handle and on error, a negative value.
+
+For more details, see SEV spec Section 6.2.
+
+2. KVM_SEV_LAUNCH_UPDATE_DATA
+
+Parameters (in): struct  kvm_sev_launch_update
+Returns: 0 on success, -negative on error
+
+The KVM_SEV_LAUNCH_UPDATE_DATA is used for encrypting the guest memory regions
+with the encryption context created using KVM_SEV_LAUNCH_START.
+
+struct kvm_sev_launch_update {
+	/* userspace address need to be encrypted (must be 16-byte aligned) */
+	__u64 uaddr;
+
+	/* length of the data to be encrypted (must be 16-byte aligned) */
+	__u32 len;
+};
+
+For more details, see SEV spec Section 6.3.
+
+3. KVM_SEV_LAUNCH_MEASURE
+
+Parameters (in): struct  kvm_sev_launch_measure
+Returns: 0 on success, -negative on error
+
+The KVM_SEV_LAUNCH_MEASURE command is used to retrieve the measurement of the
+memory regions encrypted using KVM_SEV_LAUNCH_UPDATE_DATA.
+
+struct kvm_sev_launch_measure {
+	/* where to copy the measurement */
+	__u64 uaddr;
+
+	/* length of measurement blob */
+	__u32 len;
+};
+
+For more details on how the measurement can be used for attesation, see SEV
+spec Section 6.4.
+
+4. KVM_SEV_LAUNCH_FINISH
+
+Returns: 0 on success, -negative on error
+
+KVM_SEV_LAUNCH_FINISH command finalize the SEV guest launch process.
+
+5. KVM_SEV_GUEST_STATUS
+
+Parameters (out): struct kvm_sev_guest_status
+Returns: 0 on success, -negative on error
+
+The KVM_SEV_GUEST_STATUS command is used to retrieve status information about an
+SEV-enabled guest..
+
+struct kvm_sev_guest_status {
+	/* guest handle */
+	__u32 handle;
+
+	/* guest policy */
+	__u32 policy;
+
+	/* guest state  (see below) */
+	__u8 state;
+};
+
+SEV guest state:
+
+enum {
+	SEV_STATE_INVALID = 0;
+	SEV_STATE_LAUNCHING,	/* guest is currently being launched */
+	SEV_STATE_SECRET,	/* guest is being launched and ready to accept the ciphertext data */
+	SEV_STATE_RUNNING,	/* guest is fully launched and running */
+	SEV_STATE_RECEIVING,	/* guest is being migrated in from another SEV machine */
+	SEV_STATE_SENDING	/* guest is getting migrated out another SEV machine */
+};
+
+6. KVM_SEV_DBG_DECRYPT
+
+Parameters (in): struct kvm_sev_dbg
+Returns: 0 on success, -negative on error
+
+The KVM_SEV_DEBUG_DECRYPT command is used for decrypting a memory region for the
+debug purposes.
+
+struct kvm_sev_dbg {
+	/* userspace address of data to decrypt */
+	__u64 src_uaddr;
+	/* userspace address of destination */
+	__u64 dst_uaddr;
+
+	/* length of memory region to decrypt */
+	__u32 len;
+};
+
+The command returns an error if guest policy does not allow debugging.
+
+7. KVM_SEV_DBG_ENCRYPT
+
+Parameters (in): struct kvm_sev_dbg
+Returns: 0 on success, -negative on error
+
+The KVM_SEV_DEBUG_ENCRYPT command is used for encrypting a plaintext using the
+VM encryption key.
+
+struct kvm_sev_dbg {
+	/* userspace address of data to encrypt */
+	__u64 src_uaddr;
+	/* userspace address of destination */
+	__u64 dst_uaddr;
+
+	/* length of memory region to encrypt */
+	__u32 len;
+};
+
+8. KVM_SEV_LAUNCH_SECRET
+
+Parameters (in): struct kvm_sev_launch_secret
+Returns: 0 on success, -negative on error
+
+Te KVM_SEV_LAUNCH_SECRET command can be used by hypevisor to inject a secret
+into the guest.
+
+struct kvm_sev_launch_secret {
+	/* userspace address containing the packet header */
+	__u64 hdr_uaddr;
+	__u32 hdr_len;
+
+	/* the guest memory region where the secret should be injected */
+	__u64 guest_uaddr;
+	__u32 guest_len;
+
+	/* the hypervisor memory region which contains the secret */
+	__u64 trans_uaddr;
+	__u32 trans_len;
+};
-- 
2.9.5