[pve-devel] [PATCH qemu-server v13 2/5] config: add AMD SEV support
Markus Frank
m.frank at proxmox.com
Mon Nov 18 12:16:57 CET 2024
This patch is for enabling AMD SEV (Secure Encrypted Virtualization)
support in QEMU.
VM-Config-Examples:
amd_sev: type=std,no-debug=1,no-key-sharing=1
amd_sev: es,no-debug=1,kernel-hashes=1
kernel-hashes, reduced-phys-bits & cbitpos correspond to the variables
with the same name in QEMU.
kernel-hashes=1 adds kernel hashes to enable measured linux kernel
launch since it is per default off for backward compatibility.
reduced-phys-bios and cbitpos are system specific and are read out by
the query-machine-capabilities c program and saved to the
/run/qemu-server/host-hw-capabilities.json file. This file is parsed
and than used by qemu-server to correctly start a AMD SEV VM.
type=std stands for standard sev to differentiate it from sev-es (es)
or sev-snp (snp) when support is upstream.
QEMU's sev-guest policy gets calculated with the parameters no-debug
& no-key-sharing. These parameters correspond to policy-bits 0 & 1.
If type is 'es' than policy-bit 2 gets set to 1 to activate SEV-ES.
Policy bit 3 (nosend) is always set to 1, because migration features
for sev are not upstream yet and are attackable.
SEV-ES is highly experimental since it could not be tested.
see coherent doc patch
Signed-off-by: Markus Frank <m.frank at proxmox.com>
Reviewed-by: Fiona Ebner <f.ebner at proxmox.com>
---
PVE/QemuServer.pm | 13 +++++-
PVE/QemuServer/CPUConfig.pm | 87 ++++++++++++++++++++++++++++++++++++-
2 files changed, 98 insertions(+), 2 deletions(-)
diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 8da1b4d2..a3446c3d 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -54,7 +54,7 @@ use PVE::QemuConfig;
use PVE::QemuServer::Helpers qw(config_aware_timeout min_version windows_version);
use PVE::QemuServer::Cloudinit;
use PVE::QemuServer::CGroup;
-use PVE::QemuServer::CPUConfig qw(print_cpu_device get_cpu_options get_cpu_bitness is_native_arch);
+use PVE::QemuServer::CPUConfig qw(print_cpu_device get_cpu_options get_cpu_bitness is_native_arch get_amd_sev_object);
use PVE::QemuServer::Drive qw(is_valid_drivename drive_is_cloudinit drive_is_cdrom drive_is_read_only parse_drive print_drive);
use PVE::QemuServer::Machine;
use PVE::QemuServer::Memory qw(get_current_memory);
@@ -359,6 +359,12 @@ my $confdesc = {
description => "Memory properties.",
format => $PVE::QemuServer::Memory::memory_fmt
},
+ 'amd-sev' => {
+ description => "Secure Encrypted Virtualization (SEV) features by AMD CPUs",
+ optional => 1,
+ format => 'pve-qemu-sev-fmt',
+ type => 'string',
+ },
balloon => {
optional => 1,
type => 'integer',
@@ -4167,6 +4173,11 @@ sub config_to_command {
}
}
+ if ($conf->{'amd-sev'}) {
+ push @$devices, '-object', get_amd_sev_object($conf->{'amd-sev'}, $conf->{bios});
+ push @$machineFlags, 'confidential-guest-support=sev0';
+ }
+
push @$cmd, @$devices;
push @$cmd, '-rtc', join(',', @$rtcFlags) if scalar(@$rtcFlags);
push @$cmd, '-machine', join(',', @$machineFlags) if scalar(@$machineFlags);
diff --git a/PVE/QemuServer/CPUConfig.pm b/PVE/QemuServer/CPUConfig.pm
index 33f7524f..e65d8c26 100644
--- a/PVE/QemuServer/CPUConfig.pm
+++ b/PVE/QemuServer/CPUConfig.pm
@@ -3,9 +3,11 @@ package PVE::QemuServer::CPUConfig;
use strict;
use warnings;
+use JSON;
+
use PVE::JSONSchema;
use PVE::Cluster qw(cfs_register_file cfs_read_file);
-use PVE::Tools qw(get_host_arch);
+use PVE::Tools qw(run_command get_host_arch);
use PVE::QemuServer::Helpers qw(min_version);
use base qw(PVE::SectionConfig Exporter);
@@ -15,6 +17,7 @@ print_cpu_device
get_cpu_options
get_cpu_bitness
is_native_arch
+get_amd_sev_object
);
# under certain race-conditions, this module might be loaded before pve-cluster
@@ -225,6 +228,37 @@ my $cpu_fmt = {
},
};
+my $sev_fmt = {
+ type => {
+ description => "Enable standard SEV with type='std' or enable"
+ ." experimental SEV-ES with the 'es' option.",
+ type => 'string',
+ default_key => 1,
+ format_description => "sev-type",
+ enum => ['std', 'es'],
+ maxLength => 3,
+ },
+ 'no-debug' => {
+ description => "Sets policy bit 0 to 1 to disallow debugging of guest",
+ type => 'boolean',
+ default => 0,
+ optional => 1,
+ },
+ 'no-key-sharing' => {
+ description => "Sets policy bit 1 to 1 to disallow key sharing with other guests",
+ type => 'boolean',
+ default => 0,
+ optional => 1,
+ },
+ "kernel-hashes" => {
+ description => "Add kernel hashes to guest firmware for measured linux kernel launch",
+ type => 'boolean',
+ default => 0,
+ optional => 1,
+ },
+};
+PVE::JSONSchema::register_format('pve-qemu-sev-fmt', $sev_fmt);
+
PVE::JSONSchema::register_format('pve-phys-bits', \&parse_phys_bits);
sub parse_phys_bits {
my ($str, $noerr) = @_;
@@ -773,6 +807,57 @@ sub get_cpu_bitness {
die "unsupported architecture '$arch'\n";
}
+sub get_hw_capabilities {
+ # Get reduced-phys-bits & cbitpos from host-hw-capabilities.json
+ # TODO: Find better location than /run/qemu-server/
+ my $filename = '/run/qemu-server/host-hw-capabilities.json';
+ if (! -e $filename) {
+ die "$filename does not exist. Please check the status of query-machine-capabilities: "
+ ."systemctl status query-machine-capabilities\n";
+ }
+ my $json_text = PVE::Tools::file_get_contents($filename);
+ ($json_text) = $json_text =~ /(.*)/; # untaint json text
+ my $hw_capabilities = eval { decode_json($json_text) };
+ if (my $err = $@) {
+ die $err;
+ }
+ return $hw_capabilities;
+}
+
+sub get_amd_sev_object {
+ my ($amd_sev, $bios) = @_;
+
+ my $amd_sev_conf = PVE::JSONSchema::parse_property_string($sev_fmt, $amd_sev);
+ my $sev_hw_caps = get_hw_capabilities()->{'amd-sev'};
+
+ if (!$sev_hw_caps->{'sev-support'}) {
+ die "Your CPU does not support AMD SEV.\n";
+ }
+ if ($amd_sev_conf->{type} eq 'es' && !$sev_hw_caps->{'sev-support-es'}) {
+ die "Your CPU does not support AMD SEV-ES.\n";
+ }
+ if (!$bios || $bios ne 'ovmf') {
+ die "To use AMD SEV, you need to change the BIOS to OVMF.\n";
+ }
+
+ my $sev_mem_object = 'sev-guest,id=sev0';
+ $sev_mem_object .= ',cbitpos='.$sev_hw_caps->{cbitpos};
+ $sev_mem_object .= ',reduced-phys-bits='.$sev_hw_caps->{'reduced-phys-bits'};
+
+ # guest policy bit calculation as described here:
+ # https://documentation.suse.com/sles/15-SP5/html/SLES-amd-sev/article-amd-sev.html#table-guestpolicy
+ my $policy = 0b0000;
+ $policy += 0b0001 if $amd_sev_conf->{'no-debug'};
+ $policy += 0b0010 if $amd_sev_conf->{'no-key-sharing'};
+ $policy += 0b0100 if $amd_sev_conf->{type} eq 'es';
+ # disable migration with bit 3 nosend to prevent amd-sev-migration-attack
+ $policy += 0b1000;
+
+ $sev_mem_object .= ',policy='.sprintf("%#x", $policy);
+ $sev_mem_object .= ',kernel-hashes=on' if ($amd_sev_conf->{'kernel-hashes'});
+ return $sev_mem_object;
+}
+
__PACKAGE__->register();
__PACKAGE__->init();
--
2.39.5
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