diff --git a/qm.adoc b/qm.adoc index b550888..bf53e11 100644 --- a/qm.adoc +++ b/qm.adoc @@ -715,6 +715,109 @@ 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 +^^^^^^^ + +SEV (Secure Encrypted Virtualization) enables memory encryption per VM using +AES-128 encryption and the AMD Secure Processor. + +SEV-ES (Secure Encrypted Virtualization-Encrypted State) in addition encrypts +all CPU register contents when a VM stops running, to prevent leakage of +information to the hypervisor. This feature is very experimental. + +*Host Requirements:* + +* AMD EPYC CPU +* SEV-ES is only supported on AMD EPYC 7xx2 and newer +* configure AMD memory encryption in the BIOS settings of the 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 to 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 the host 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: +[...] SEV supported: ASIDs +[...] SEV-ES supported: ASIDs +# cat /sys/module/kvm_amd/parameters/sev +Y +---- + +*Guest Requirements:* + +* edk2-OVMF +* advisable to use Q35 +* The guest operating system must contain SEV-support. + +*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 +* PCI passthrough is not supported. +* SEV-ES is very experimental. +* QEMU & AMD-SEV documentation is very limited. + +Example Configuration: + +---- +# qm set -amd_sev type=std,no-debug=1,no-key-sharing=1,kernel-hashes=1 +---- + +The *type* defines the encryption technology ("type=" is not necessary). +Available options are std & es. + +The QEMU *policy* parameter gets calculated with the *no-debug* and +*no-key-sharing* parameters. These parameters correspond to policy-bit 0 and 1. +If *type* is *es* the policy-bit 2 is set to 1 so that SEV-ES is enabled. +Policy-bit 3 (nosend) is always set to 1 to prevent migration-attacks. For more +information on how to calculate the policy see: +https://www.amd.com/system/files/TechDocs/55766_SEV-KM_API_Specification.pdf[AMD SEV API Specification Chapter 3] + +The *kernel-hashes* option is off per default for backward compatibility with +older OVMF images and guests that do not measure the kernel/initrd. +See https://lists.gnu.org/archive/html/qemu-devel/2021-11/msg02598.html + +*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://developer.amd.com/sev/ +* 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 [[qm_network_device]] Network Device