This patch is for enabling AMD SEV-SNP support. Where applicable, it extends support for existing SEV(-ES) variables to SEV-SNP. This means that it retains no-debug and kernel-hashes options, but the no-key-sharing option is removed.
The default policy value is identical to QEMU’s, and the therefore required option has been added to configure SMT support. The code was tested by running a VM without SEV, with SEV, SEV-ES, SEV-SNP. Each configuration was tested with and without an EFI disk attached. For SEV-enabled configurations it was also verified that the kernel actually used the respective feature. Signed-off-by: Philipp Giersfeld <philipp.giersf...@canarybit.eu> Reviewed-by: Daniel Kral <d.kral at proxmox.com> --- changes since v1: https://lists.proxmox.com/pipermail/pve-devel/2025-February/068159.html * Fix formatting and code layout * Fix bug in policy calculation Signed-off-by: Philipp Giersfeld <philipp.giersf...@canarybit.eu> --- PVE/API2/Qemu.pm | 7 +++- PVE/QemuServer.pm | 49 +++++++++++++++++++-------- PVE/QemuServer/CPUConfig.pm | 66 ++++++++++++++++++++++++++++--------- 3 files changed, 92 insertions(+), 30 deletions(-) diff --git a/PVE/API2/Qemu.pm b/PVE/API2/Qemu.pm index 295260e7..4f48cf85 100644 --- a/PVE/API2/Qemu.pm +++ b/PVE/API2/Qemu.pm @@ -548,8 +548,13 @@ my sub create_disks : prototype($$$$$$$$$$$) { my $volid; if ($ds eq 'efidisk0') { my $smm = PVE::QemuServer::Machine::machine_type_is_q35($conf); + + my $amd_sev_type = PVE::QemuServer::CPUConfig::get_amd_sev_type($conf); + die "SEV-SNP uses consolidated read-only firmware" + if $amd_sev_type && $amd_sev_type eq 'snp'; + ($volid, $size) = PVE::QemuServer::create_efidisk( - $storecfg, $storeid, $vmid, $fmt, $arch, $disk, $smm); + $storecfg, $storeid, $vmid, $fmt, $arch, $disk, $smm, $amd_sev_type); } elsif ($ds eq 'tpmstate0') { # swtpm can only use raw volumes, and uses a fixed size $size = PVE::Tools::convert_size(PVE::QemuServer::Drive::TPMSTATE_DISK_SIZE, 'b' => 'kb'); diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm index 808c0e1c..51e551b8 100644 --- a/PVE/QemuServer.pm +++ b/PVE/QemuServer.pm @@ -52,7 +52,7 @@ use PVE::QemuConfig; use PVE::QemuServer::Helpers qw(config_aware_timeout min_version kvm_user_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 get_amd_sev_object); +use PVE::QemuServer::CPUConfig qw(print_cpu_device get_cpu_options get_cpu_bitness is_native_arch get_amd_sev_object get_amd_sev_type); use PVE::QemuServer::Drive qw(is_valid_drivename checked_volume_format 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); @@ -88,6 +88,13 @@ my $OVMF = { "$EDK2_FW_BASE/OVMF_CODE_4M.secboot.fd", "$EDK2_FW_BASE/OVMF_VARS_4M.ms.fd", ], + '4m-sev' => [ + "$EDK2_FW_BASE/OVMF_CVM_CODE_4M.fd", + "$EDK2_FW_BASE/OVMF_CVM_VARS_4M.fd", + ], + '4m-snp' => [ + "$EDK2_FW_BASE/OVMF_CVM_4M.fd", + ], # FIXME: These are legacy 2MB-sized images that modern OVMF doesn't supports to build # anymore. how can we deperacate this sanely without breaking existing instances, or using # older backups and snapshot? @@ -3172,15 +3179,22 @@ sub vga_conf_has_spice { return $1 || 1; } -sub get_ovmf_files($$$) { - my ($arch, $efidisk, $smm) = @_; +sub get_ovmf_files($$$$) { + my ($arch, $efidisk, $smm, $amd_sev_type) = @_; my $types = $OVMF->{$arch} or die "no OVMF images known for architecture '$arch'\n"; my $type = 'default'; if ($arch eq 'x86_64') { - if (defined($efidisk->{efitype}) && $efidisk->{efitype} eq '4m') { + if ($amd_sev_type && $amd_sev_type eq 'snp') { + $type = "4m-snp"; + my ($ovmf) = $types->{$type}->@*; + die "EFI base image '$ovmf' not found\n" if ! -f $ovmf; + return ($ovmf); + } elsif ($amd_sev_type) { + $type = "4m-sev"; + } elsif (defined($efidisk->{efitype}) && $efidisk->{efitype} eq '4m') { $type = $smm ? "4m" : "4m-no-smm"; $type .= '-ms' if $efidisk->{'pre-enrolled-keys'}; } else { @@ -3329,7 +3343,8 @@ my sub print_ovmf_drive_commandlines { my $d = $conf->{efidisk0} ? parse_drive('efidisk0', $conf->{efidisk0}) : undef; - my ($ovmf_code, $ovmf_vars) = get_ovmf_files($arch, $d, $q35); + my $amd_sev_type = get_amd_sev_type($conf); + my ($ovmf_code, $ovmf_vars) = get_ovmf_files($arch, $d, $q35, $amd_sev_type); my $var_drive_str = "if=pflash,unit=1,id=drive-efidisk0"; if ($d) { @@ -3526,10 +3541,17 @@ sub config_to_command { die "OVMF (UEFI) BIOS is not supported on 32-bit CPU types\n" if !$forcecpu && get_cpu_bitness($conf->{cpu}, $arch) == 32; - my ($code_drive_str, $var_drive_str) = - print_ovmf_drive_commandlines($conf, $storecfg, $vmid, $arch, $q35, $version_guard); - push $cmd->@*, '-drive', $code_drive_str; - push $cmd->@*, '-drive', $var_drive_str; + my $amd_sev_type = get_amd_sev_type($conf); + if ($amd_sev_type && $amd_sev_type eq 'snp') { + my $arch = PVE::QemuServer::Helpers::get_vm_arch($conf); + my $d = $conf->{efidisk0} ? parse_drive('efidisk0', $conf->{efidisk0}) : undef; + push $cmd->@*, '-bios', get_ovmf_files($arch, $d, undef, $amd_sev_type); + } else { + my ($code_drive_str, $var_drive_str) = print_ovmf_drive_commandlines( + $conf, $storecfg, $vmid, $arch, $q35, $version_guard); + push $cmd->@*, '-drive', $code_drive_str; + push $cmd->@*, '-drive', $var_drive_str; + } } if ($q35) { # tell QEMU to load q35 config early @@ -8337,7 +8359,8 @@ sub get_efivars_size { my $arch = PVE::QemuServer::Helpers::get_vm_arch($conf); $efidisk //= $conf->{efidisk0} ? parse_drive('efidisk0', $conf->{efidisk0}) : undef; my $smm = PVE::QemuServer::Machine::machine_type_is_q35($conf); - my (undef, $ovmf_vars) = get_ovmf_files($arch, $efidisk, $smm); + my $amd_sev_type = get_amd_sev_type($conf); + my (undef, $ovmf_vars) = get_ovmf_files($arch, $efidisk, $smm, $amd_sev_type); return -s $ovmf_vars; } @@ -8361,10 +8384,10 @@ sub update_tpmstate_size { $conf->{tpmstate0} = print_drive($disk); } -sub create_efidisk($$$$$$$) { - my ($storecfg, $storeid, $vmid, $fmt, $arch, $efidisk, $smm) = @_; +sub create_efidisk($$$$$$$$) { + my ($storecfg, $storeid, $vmid, $fmt, $arch, $efidisk, $smm, $amd_sev_type) = @_; - my (undef, $ovmf_vars) = get_ovmf_files($arch, $efidisk, $smm); + my (undef, $ovmf_vars) = get_ovmf_files($arch, $efidisk, $smm, $amd_sev_type); my $vars_size_b = -s $ovmf_vars; my $vars_size = PVE::Tools::convert_size($vars_size_b, 'b' => 'kb'); diff --git a/PVE/QemuServer/CPUConfig.pm b/PVE/QemuServer/CPUConfig.pm index ad0be16e..94a00a4e 100644 --- a/PVE/QemuServer/CPUConfig.pm +++ b/PVE/QemuServer/CPUConfig.pm @@ -18,6 +18,7 @@ get_cpu_options get_cpu_bitness is_native_arch get_amd_sev_object +get_amd_sev_type ); # under certain race-conditions, this module might be loaded before pve-cluster @@ -231,25 +232,32 @@ my $cpu_fmt = { my $sev_fmt = { type => { description => "Enable standard SEV with type='std' or enable" - ." experimental SEV-ES with the 'es' option.", + ." experimental SEV-ES with the 'es' option or enable " + ."experimental SEV-SNP with the 'snp' option.", type => 'string', default_key => 1, format_description => "sev-type", - enum => ['std', 'es'], + enum => ['std', 'es', 'snp'], maxLength => 3, }, 'no-debug' => { - description => "Sets policy bit 0 to 1 to disallow debugging of guest", + description => "Sets policy bit 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", + description => "Sets policy bit to disallow key sharing with other guests", type => 'boolean', default => 0, optional => 1, }, + 'allow-smt' => { + description => "Sets policy bit to allow Simultaneous Multi Threading (SMT)", + type => 'boolean', + default => 1, + optional => 1, + }, "kernel-hashes" => { description => "Add kernel hashes to guest firmware for measured linux kernel launch", type => 'boolean', @@ -823,6 +831,13 @@ sub get_hw_capabilities { } return $hw_capabilities; } +sub get_amd_sev_type { + my ($conf) = @_; + + return undef if !$conf->{'amd-sev'}; + + return PVE::JSONSchema::parse_property_string($sev_fmt, $conf->{'amd-sev'})->{type}; +} sub get_amd_sev_object { my ($amd_sev, $bios) = @_; @@ -836,22 +851,41 @@ sub get_amd_sev_object { if ($amd_sev_conf->{type} eq 'es' && !$sev_hw_caps->{'sev-support-es'}) { die "Your CPU does not support AMD SEV-ES.\n"; } + if ($amd_sev_conf->{type} eq 'snp' && !$sev_hw_caps->{'sev-support-snp'}) { + die "Your CPU does not support AMD SEV-SNP.\n"; + } if (!$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 = 0; - $policy |= 1 << 0 if $amd_sev_conf->{'no-debug'}; - $policy |= 1 << 1 if $amd_sev_conf->{'no-key-sharing'}; - $policy |= 1 << 2 if $amd_sev_conf->{type} eq 'es'; - # disable migration with bit 3 nosend to prevent amd-sev-migration-attack - $policy |= 1 << 3; + my $sev_mem_object = ''; + my $policy; + if ($amd_sev_conf->{type} eq 'es' || $amd_sev_conf->{type} eq 'std') { + $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 + $policy = 0; + $policy |= 1 << 0 if $amd_sev_conf->{'no-debug'}; + $policy |= 1 << 1 if $amd_sev_conf->{'no-key-sharing'}; + $policy |= 1 << 2 if $amd_sev_conf->{type} eq 'es'; + # disable migration with bit 3 nosend to prevent amd-sev-migration-attack + $policy |= 1 << 3; + } elsif ($amd_sev_conf->{type} eq 'snp') { + $sev_mem_object .= 'sev-snp-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 in chapter 4.3: + # https://www.amd.com/system/files/TechDocs/56860.pdf + # Reserved bit must be one + $policy = 1 << 17; + $policy |= 1 << 16 if $amd_sev_conf->{'allow-smt'}; + $policy |= 1 << 19 if !$amd_sev_conf->{'no-debug'}; + } + $sev_mem_object .= ',policy='.sprintf("%#x", $policy); $sev_mem_object .= ',kernel-hashes=on' if ($amd_sev_conf->{'kernel-hashes'}); -- 2.39.5 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
