[pve-devel] [PATCH qemu-server v5 2/3] config: QEMU AMD SEV enable
Markus Frank
m.frank at proxmox.com
Fri Apr 19 12:10:48 CEST 2024
This patch is for enabling AMD SEV (Secure Encrypted
Virtualization) support in QEMU
VM-Config-Examples:
amd_sev: type=std,nodbg=1,noks=1
amd_sev: es,nodbg=1,kernel-hashes=1
Node-Config-Example (gets generated automatically):
amd_sev: cbitpos=47,reduced-phys-bios=1
kernel-hashes, reduced-phys-bios & cbitpos correspond to the varibles
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 amd-sev-support.service on boot and saved to the /run/amd-sev-params
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 nodbg & noks
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>
---
v5:
* parse /run/amd-sev-params for hardware parameters
* removed NodeConfig dependency
* only disallow live-migration and snapshots with vmstate
-> allow offline migration and snapshots without vmstate
v4:
* reduced lines of code
* added text that SEV-ES is experimental
PVE/API2/Qemu.pm | 10 +++++
PVE/QemuMigrate.pm | 4 ++
PVE/QemuServer.pm | 102 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 116 insertions(+)
diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm
index 497987f..b35ab69 100644
--- a/PVE/API2/Qemu.pm
+++ b/PVE/API2/Qemu.pm
@@ -4490,6 +4490,10 @@ __PACKAGE__->register_method({
push $local_resources->@*, "clipboard=vnc";
}
+ if ($res->{running} && $vmconf->{amd_sev}) {
+ push $local_resources->@*, "amd_sev";
+ }
+
# if vm is not running, return target nodes where local storage/mapped devices are available
# for offline migration
if (!$res->{running}) {
@@ -5170,6 +5174,12 @@ __PACKAGE__->register_method({
die "unable to use snapshot name 'pending' (reserved name)\n"
if lc($snapname) eq 'pending';
+ my $conf = PVE::QemuConfig->load_config($vmid);
+ if ($param->{vmstate} && $conf->{amd_sev}) {
+ die "Snapshots that include memory are not supported while memory"
+ ." is encrypted by AMD SEV.\n"
+ }
+
my $realcmd = sub {
PVE::Cluster::log_msg('info', $authuser, "snapshot VM $vmid: $snapname");
PVE::QemuConfig->snapshot_create($vmid, $snapname, $param->{vmstate},
diff --git a/PVE/QemuMigrate.pm b/PVE/QemuMigrate.pm
index 8d9b35a..7db18b2 100644
--- a/PVE/QemuMigrate.pm
+++ b/PVE/QemuMigrate.pm
@@ -260,6 +260,10 @@ sub prepare {
die "VMs with 'clipboard' set to 'vnc' are not live migratable!\n";
}
+ if ($running && $conf->{'amd_sev'}) {
+ die "VMs with AMD SEV are not live migratable!\n";
+ }
+
my $vollist = PVE::QemuServer::get_vm_volumes($conf);
my $storages = {};
diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 6e2c805..e1ad190 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -185,6 +185,59 @@ my $agent_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 => "qemu-sev-type",
+ enum => ['std', 'es'],
+ maxLength => 3,
+ },
+ nodbg => {
+ description => "Sets policy bit 0 to 1 to disallow debugging of guest",
+ type => 'boolean',
+ format_description => "qemu-sev-nodbg",
+ default => 0,
+ optional => 1,
+ },
+ noks => {
+ description => "Sets policy bit 1 to 1 to disallow key sharing with other guests",
+ type => 'boolean',
+ format_description => "qemu-sev-noks",
+ default => 0,
+ optional => 1,
+ },
+ "kernel-hashes" => {
+ description => "Add kernel hashes to guest firmware for measured linux kernel launch",
+ type => 'boolean',
+ format_description => "qemu-sev-kernel-hashes",
+ default => 0,
+ optional => 1,
+ },
+};
+PVE::JSONSchema::register_format('pve-qemu-sev-fmt', $sev_fmt);
+
+my $sev_node_fmt = {
+ cbitpos => {
+ description => "C-bit: marks if a memory page is protected. System dependent",
+ type => 'integer',
+ default => 47,
+ optional => 1,
+ minimum => 0,
+ maximum => 100,
+ },
+ 'reduced-phys-bits' => {
+ description => "Number of bits the physical address space is reduced by. System dependent",
+ type => 'integer',
+ default => 1,
+ optional => 1,
+ minimum => 0,
+ maximum => 100,
+ },
+};
+
my $vga_fmt = {
type => {
description => "Select the VGA type.",
@@ -366,6 +419,12 @@ my $confdesc = {
description => "Memory properties.",
format => $PVE::QemuServer::Memory::memory_fmt
},
+ amd_sev => {
+ description => "Secure Encrypted Virtualization (SEV) features by AMD CPUs",
+ optional => 1,
+ format => 'pve-qemu-sev-fmt',
+ type => 'string',
+ },
balloon => {
optional => 1,
type => 'integer',
@@ -4084,6 +4143,39 @@ sub config_to_command {
}
push @$machineFlags, "type=${machine_type_min}";
+ if ($conf->{amd_sev}) {
+ if ($conf->{bios} && $conf->{bios} ne 'ovmf') {
+ die "For using SEV you need to change your guest bios to ovmf.\n";
+ }
+
+ my $amd_sev_conf = parse_property_string($sev_fmt, $conf->{amd_sev});
+ my $sev_hw_params = get_sev_hw_parameters();
+
+ if (!$sev_hw_params->{sev}) {
+ die "Your CPU does not support AMD SEV!\n";
+ }
+ if ($amd_sev_conf->{type} eq 'es' && !$sev_hw_params->{'sev-es'}) {
+ die "Your CPU does not support AMD SEV-ES!\n";
+ }
+
+ my $sev_mem_object = 'sev-guest,id=sev0'
+ .',cbitpos='.$sev_hw_params->{cbitpos}
+ .',reduced-phys-bits='.$sev_hw_params->{'reduced-phys-bits'};
+
+ my $policy = 0b0;
+ $policy += 0b1 if ($amd_sev_conf->{nodbg});
+ $policy += 0b10 if ($amd_sev_conf->{noks});
+ $policy += 0b100 if ($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'});
+
+ push @$devices, '-object' , $sev_mem_object;
+ push @$machineFlags, 'confidential-guest-support=sev0';
+ }
+
push @$cmd, @$devices;
push @$cmd, '-rtc', join(',', @$rtcFlags) if scalar(@$rtcFlags);
push @$cmd, '-machine', join(',', @$machineFlags) if scalar(@$machineFlags);
@@ -4127,6 +4219,16 @@ sub check_rng_source {
}
}
+sub get_sev_hw_parameters {
+ # Get reduced-phys-bits & cbitpos from /run/amd-sev-params
+ my $filename = '/run/amd-sev-params';
+ open my $fh, '<', $filename or die "Could not open '$filename' for reading: $!";
+ my $json_text = do { local $/; <$fh> };
+ close $fh;
+ my $sev_params = JSON->new->decode($json_text);
+ return $sev_params;
+}
+
sub spice_port {
my ($vmid) = @_;
--
2.39.2
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