[pve-devel] [PATCH qemu-server] QEMU AMD SEV enable
Markus Frank
m.frank at proxmox.com
Thu Jun 9 13:14:07 CEST 2022
This Patch is for enabling AMD SEV (Secure Encrypted Virtualization) support in
QEMU and for supporting other memory encryption technologies like INTEL MKTME
(Multi-key Total Memory Encryption) and AMD-SNP in the future.
Config-Example:
memory_encryption: type=sev,cbitpos=47,policy=0x0005,reduced-phys-bits=1
"reduced-phys-bios" and "cbitpos" are system specific and can be read out with
QMP. If not set by the user, a dummy-vm gets started to read QMP for these
variables out and save them to config. Afterwards, the dummy-vm gets stopped.
For a more detailed Explanation plus Requirements & Limitations
see my coherent pve-docs patch and the qemu documentation.
Signed-off-by: Markus Frank <m.frank at proxmox.com>
---
I could not test SEV-ES because I get a similar error to
https://www.mail-archive.com/devel@edk2.groups.io/msg38521.html
But I still get the same error on master and mentioned patched versions.
On some older versions I just get "kvm: SEV-ES reset address is zero
kvm: failed to locate and/or save reset vector"
Maybe I will report my error to the edk2 project or find a way to fix
it, when I know more about it.
I also could not test SEV-SNP, because I do not have a EPYC 7003 to test
on and there is also no support in the Linux Kernel yet. SEV-SNP support
should be in Linux 5.19:
https://www.phoronix.com/scan.php?page=news_item&px=AMD-SEV-SNP-Arrives-Linux-5.19
patched kernel-fork: https://github.com/AMDESE/linux/tree/sev-snp-5.18-rc3
PVE/QemuServer.pm | 133 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 133 insertions(+)
diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index e9aa248..abc21d4 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -174,6 +174,55 @@ my $agent_fmt = {
},
};
+my $memory_encryption_fmt = {
+ type => {
+ type => 'string',
+ default_key => 1,
+ description => "Memory Encryption Type:"
+ ."for AMD SEV -> 'memory_encryption: type=sev'"
+ ."for AMD SEV-SNP -> 'memory_encryption: type=sev-snp'"
+ ."for AMD SEV-ES -> use 'sev' and change policy to between 0x4 and 0x7"
+ ."(Bit-2 has to be set 1 (LSB 0 bit numbering))"
+ ."(sev requires edk2-ovmf & on guest: up-to-date kernel + sev support &"
+ ."on host: add kernel-parameters 'mem_encrypt=on kvm_amd.sev=1')"
+ ."see https://github.com/AMDESE/AMDSEV",
+ format_description => "qemu-memory-encryption-type",
+ #pattern => '(sev|sev-snp|mktme)',
+ pattern => '(sev|sev-snp)',
+ default => "",
+ maxLength => 10,
+ },
+ 'reduced-phys-bits' => {
+ description => "Number of bits the physical address space is reduced by. System dependent",
+ type => 'integer',
+ default => 1,
+ optional => 1,
+ minium => 0,
+ maximum => 100,
+ },
+ cbitpos => {
+ description => "C-bit: marks if a memory page is protected. System dependent",
+ type => 'integer',
+ default => 47,
+ optional => 1,
+ minium => 0,
+ maximum => 100,
+ },
+ policy => {
+ description => "SEV Guest Policy"
+ ."see Capter 3:"
+ ."https://www.amd.com/system/files/TechDocs/55766_SEV-KM_API_Specification.pdf"
+ ."& https://www.qemu.org/docs/master/system/i386/amd-memory-encryption.html",
+ format_description => "qemu-memory-encryption-policy",
+ type => 'string',
+ default => '0x0000',
+ pattern => '0[xX][0-9a-fA-F]{1,4}',
+ optional => 1,
+ maxLength => 6,
+ },
+};
+PVE::JSONSchema::register_format('pve-qemu-memory-encryption-fmt', $memory_encryption_fmt);
+
my $vga_fmt = {
type => {
description => "Select the VGA type.",
@@ -348,6 +397,12 @@ my $confdesc = {
minimum => 16,
default => 512,
},
+ memory_encryption => {
+ description => "Memory Encryption",
+ optional => 1,
+ format => 'pve-qemu-memory-encryption-fmt',
+ type => 'string',
+ },
balloon => {
optional => 1,
type => 'integer',
@@ -2107,6 +2162,16 @@ sub parse_guest_agent {
return $res;
}
+sub parse_memory_encryption {
+ my ($value) = @_;
+
+ return if !$value;
+
+ my $res = eval { parse_property_string($memory_encryption_fmt, $value) };
+ warn $@ if $@;
+ return $res;
+}
+
sub get_qga_key {
my ($conf, $key) = @_;
return undef if !defined($conf->{agent});
@@ -4079,6 +4144,74 @@ sub config_to_command {
}
push @$machineFlags, "type=${machine_type_min}";
+ # Memory Encryption configuration
+ my $memory_encryption = parse_memory_encryption($conf->{'memory_encryption'});
+
+ # Die if bios is not ovmf
+ if (
+ $conf->{'memory_encryption'}
+ && $memory_encryption->{type} eq 'sev'
+ && !$conf->{bios} eq 'ovmf'
+ ) {
+ die "SEV needs ovmf";
+ }
+
+ # AMD SEV
+ if ($conf->{'memory_encryption'} && $memory_encryption->{type} =~ /(sev|sev-snp)/) {
+ # Get reduced-phys-bits & cbitpos from QMP, if not set
+ if (
+ !$memory_encryption->{'reduced-phys-bits'}
+ || !$memory_encryption->{cbitpos}
+ ) {
+ my $fakevmid = -1;
+ my $qemu_cmd = get_command_for_arch($arch);
+ my $pidfile = PVE::QemuServer::Helpers::pidfile_name($fakevmid);
+ my $default_machine = $default_machines->{$arch};
+ my $cmd = [
+ $qemu_cmd,
+ '-machine', $default_machine,
+ '-display', 'none',
+ '-chardev', "socket,id=qmp,path=/var/run/qemu-server/$fakevmid.qmp,server=on,wait=off",
+ '-mon', 'chardev=qmp,mode=control',
+ '-pidfile', $pidfile,
+ '-S', '-daemonize'
+ ];
+ if (!$kvm) {
+ push @$cmd, '-accel', 'tcg';
+ }
+ my $rc = run_command($cmd, noerr => 1, quiet => 0);
+ die "QEMU flag querying VM exited with code " . $rc if $rc;
+ my $res = mon_cmd($fakevmid, 'query-sev-capabilities');
+ $memory_encryption->{'reduced-phys-bits'} = $res->{'reduced-phys-bits'};
+ $memory_encryption->{cbitpos} = $res->{cbitpos};
+ $conf->{'memory_encryption'} = PVE::JSONSchema::print_property_string(
+ $memory_encryption,
+ $memory_encryption_fmt
+ );
+ PVE::QemuConfig->write_config($vmid, $conf);
+ vm_stop(undef, $fakevmid, 1, 1, 10, 0, 1);
+ }
+
+ # qemu-Example: -object 'sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=1';
+ # see https://www.qemu.org/docs/master/system/i386/amd-memory-encryption.html
+ my $memobjcmd = "";
+ if ($memory_encryption->{type} eq 'sev-snp') {
+ # https://github.com/AMDESE/AMDSEV/tree/sev-snp-devel
+ $memobjcmd = $memobjcmd.'sev-snp-guest,';
+ } else {
+ $memobjcmd = $memobjcmd.'sev-guest,';
+ }
+ $memobjcmd = $memobjcmd . 'id=sev0,cbitpos='.$memory_encryption->{cbitpos}
+ .',reduced-phys-bits='.$memory_encryption->{'reduced-phys-bits'};
+ if ($memory_encryption->{type} eq 'sev' && $memory_encryption->{policy}) {
+ $memobjcmd = $memobjcmd.',policy='.$memory_encryption->{policy}
+ }
+ push @$devices, '-object' , $memobjcmd;
+ # old qemu-Example: -machine 'type=q35+pve0,memory-encryption=sev0'
+ # https://fossies.org/linux/qemu/docs/system/confidential-guest-support.rst
+ push @$machineFlags, 'confidential-guest-support=sev0';
+ }
+
push @$cmd, @$devices;
push @$cmd, '-rtc', join(',', @$rtcFlags) if scalar(@$rtcFlags);
push @$cmd, '-machine', join(',', @$machineFlags) if scalar(@$machineFlags);
--
2.30.2
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