[pve-devel] [PATCH docs v2 2/2] added Memory Encryption documentation

[Markus Frank]

added AMD SEV documentation for "[PATCH qemu-server] QEMU AMD SEV
enable"

Signed-off-by: Markus Frank <m.frank at proxmox.com>
---
 qm.adoc | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)

diff --git a/qm.adoc b/qm.adoc
index e7d0c07..5ba43a2 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -598,6 +598,119 @@ systems.
 When allocating RAM to your VMs, a good rule of thumb is always to leave 1GB
 of RAM available to the host.
 
+[[qm_memory_encryption]]
+Memory Encryption
+~~~~~~~~~~~~~~~~~
+
+[[qm_memory_encryption_sev]]
+AMD SEV
+^^^^^^^
+
+Memory Encryption per VM using AES-128 Encryption and the AMD Secure Processor.
+See https://developer.amd.com/sev/[AMD SEV]
+
+*Host-Requirements:*
+
+* AMD EPYC/Ryzen PRO CPU
+* configured SEV BIOS settings on Host Machine
+* add "kvm_amd.sev=1" to kernel parameters if not enabled by default
+* add "mem_encrypt=on" to kernel parameters if you want encrypt memory on the
+host (SME)
+see https://www.kernel.org/doc/Documentation/x86/amd-memory-encryption.txt
+* maybe increase SWIOTLB see https://github.com/AMDESE/AMDSEV#faq-4
+
+To check if SEV is enabled on Host-Machine search for `sev` in dmesg
+and print out the sev kernel parameter of kvm_amd:
+
+----
+# dmesg | grep -i sev
+[...] ccp 0000:45:00.1: sev enabled
+[...] ccp 0000:45:00.1: SEV API: <buildversion>
+[...] SEV supported: <number> ASIDs
+[...] SEV-ES supported: <number> ASIDs
+# cat /sys/module/kvm_amd/parameters/sev
+Y
+----
+
+*Guest-VM-Requirements:*
+
+* edk2-OVMF
+* advisable to use Q35
+* The guest operating system inside the VM must contain SEV-support
+* if there are problems while booting (stops at blank/splash screen or "Guest has not
+initialized the display (yet)") try to add virtio-rng and/or set "freeze: 1"
+so that you wait a few seconds before you click on *Resume* to boot.
+
+*Limitations:*
+
+* Because the memory is encrypted the memory usage on host is always wrong
+* Operations that involve saving or restoring memory like snapshots
+& live migration do not work yet or are attackable
+https://github.com/PSPReverse/amd-sev-migration-attack
+* KVM is unsupported when running as an SEV guest
+* PCI passthrough is not supported
+
+Example Configuration:
+
+----
+# qm set <vmid> -memory_encryption type=sev,cbitpos=47,policy=0x0001,reduced-phys-bits=1
+----
+
+*SEV Parameters*
+
+*type* defines the encryption technology ("type=" is not necessary):
+currently-supported: *sev*
+and in the future: sev-snp, mktme
+
+*reduced-phys-bios*, *cbitpos* and *policy* correspond to the variables with the
+same name in qemu.
+
+*reduced-phys-bios* and *cbitpos* are system specific and can be read out
+with QMP. If not set, qm starts a dummy-vm to read QMP
+for these variables out and saves them to config.
+
+*policy* can be calculated with
+https://www.amd.com/system/files/TechDocs/55766_SEV-KM_API_Specification.pdf[AMD SEV API Specification Chapter 3]
+
+To use SEV-ES (CPU register encryption) the *policy* should be set
+somewhere between 0x4 and 0x7 or 0xC and 0xF, etc.
+(Bit-2 has to be set 1 (LSB 0 bit numbering))
+
+*Check if SEV is working on the Guest*
+
+Method 1 - dmesg:
+
+Output should look like this.
+
+----
+# dmesg | grep -i sev
+AMD Memory Encryption Features active: SEV
+----
+
+Method 2 - MSR 0xc0010131 (MSR_AMD64_SEV):
+
+Output should be 1.
+
+----
+# apt install msr-tools
+# modprobe msr
+# rdmsr -a 0xc0010131
+1
+----
+
+Links:
+
+* https://github.com/AMDESE/AMDSEV
+* https://www.qemu.org/docs/master/system/i386/amd-memory-encryption.html
+* https://www.amd.com/system/files/TechDocs/55766_SEV-KM_API_Specification.pdf
+* https://documentation.suse.com/sles/15-SP1/html/SLES-amd-sev/index.html
+
+// Commented because cannot be tested without new EPYC-CPU
+// AMD SEV-SNP
+// ^^^^^^^^^^^
+// * SEV-SNP needs EPYC 7003 "Milan" processors.
+// * SEV-SNP should in Kernel 5.19:
+// https://www.phoronix.com/scan.php?page=news_item&px=AMD-SEV-SNP-Arrives-Linux-5.19
 
 [[qm_network_device]]
 Network Device
-- 
2.30.2