[pve-devel] [PATCH qemu-server v5 1/3] add C program to get AMD SEV hardware parameters from CPUID

[pve-devel] [PATCH qemu-server v5 1/3] add C program to get AMD SEV hardware parameters from CPUID

[Markus Frank]

Implement a systemd service that runs a C program that extracts AMD SEV
hardware parameters such as reduced-phys-bios and cbitpos from CPUID at boot
time, verifies that SEV, SEV-ES & SEV-SNP are enabled, and outputs these details
as JSON to /run/amd-sev-params.

Signed-off-by: Markus Frank <m.frank@proxmox.com>
---
 Makefile                                |  1 +
 amd-sev-support/Makefile                | 21 +++++++++++
 amd-sev-support/amd-sev-support.c       | 48 +++++++++++++++++++++++++
 amd-sev-support/amd-sev-support.service | 12 +++++++
 4 files changed, 82 insertions(+)
 create mode 100644 amd-sev-support/Makefile
 create mode 100644 amd-sev-support/amd-sev-support.c
 create mode 100644 amd-sev-support/amd-sev-support.service

diff --git a/Makefile b/Makefile
index 133468d..ccd12a1 100644
--- a/Makefile
+++ b/Makefile
@@ -65,6 +65,7 @@ install: $(PKGSOURCES)
 	install -m 0644 -D bootsplash.jpg $(DESTDIR)/usr/share/$(PACKAGE)
 	$(MAKE) -C PVE install
 	$(MAKE) -C qmeventd install
+	$(MAKE) -C amd-sev-support install
 	$(MAKE) -C qemu-configs install
 	$(MAKE) -C vm-network-scripts install
 	install -m 0755 qm $(DESTDIR)$(SBINDIR)
diff --git a/amd-sev-support/Makefile b/amd-sev-support/Makefile
new file mode 100644
index 0000000..022ed94
--- /dev/null
+++ b/amd-sev-support/Makefile
@@ -0,0 +1,21 @@
+DESTDIR=
+PREFIX=/usr
+SBINDIR=${PREFIX}/libexec/qemu-server
+SERVICEDIR=/lib/systemd/system
+
+CC ?= gcc
+CFLAGS += -O2 -fanalyzer -Werror -Wall -Wextra -Wpedantic -Wtype-limits -Wl,-z,relro -std=gnu11
+
+amd-sev-support: amd-sev-support.c
+	$(CC) $(CFLAGS) -o $@ $< $(LDFLAGS)
+
+.PHONY: install
+install: amd-sev-support
+	install -d ${DESTDIR}/${SBINDIR}
+	install -d ${DESTDIR}${SERVICEDIR}
+	install -m 0644 amd-sev-support.service ${DESTDIR}${SERVICEDIR}
+	install -m 0755 amd-sev-support ${DESTDIR}${SBINDIR}
+
+.PHONY: clean
+clean:
+	rm -f amd-sev-support
diff --git a/amd-sev-support/amd-sev-support.c b/amd-sev-support/amd-sev-support.c
new file mode 100644
index 0000000..73a7bd8
--- /dev/null
+++ b/amd-sev-support/amd-sev-support.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+int main() {
+    uint32_t eax, ebx, ecx, edx;
+
+    // query Encrypted Memory Capabilities, see:
+    // https://en.wikipedia.org/wiki/CPUID#EAX=8000001Fh:_Encrypted_Memory_Capabilities
+    uint32_t query_function = 0x8000001F;
+    asm volatile("cpuid"
+	 : "=a"(eax), "=b"(ebx), "=c"(ecx), "=d"(edx)
+	 : "0"(query_function)
+    );
+
+    bool sev_support = (eax & (1<<1)) != 0;
+    bool sev_es_support = (eax & (1<<3)) != 0;
+    bool sev_snp_support = (eax & (1<<4)) != 0;
+
+    uint8_t cbitpos = ebx & 0x3f;
+    uint8_t reduced_phys_bits = (ebx >> 6) & 0x3f;
+
+    FILE *file;
+    char *filename = "/run/amd-sev-params";
+
+    file = fopen(filename, "w");
+    if (file == NULL) {
+	perror("Error opening file");
+	return 1;
+    }
+
+    fprintf(file, "{"
+	" \"cbitpos\": %u,"
+	" \"reduced-phys-bits\": %u,"
+	" \"sev\": %s,"
+	" \"sev-es\": %s,"
+	" \"sev-snp\": %s"
+	" }\n",
+	cbitpos,
+	reduced_phys_bits,
+	sev_support ? "true" : "false",
+	sev_es_support ? "true" : "false",
+	sev_snp_support ? "true" : "false"
+    );
+
+    fclose(file);
+    return 0;
+}
diff --git a/amd-sev-support/amd-sev-support.service b/amd-sev-support/amd-sev-support.service
new file mode 100644
index 0000000..466dd0a
--- /dev/null
+++ b/amd-sev-support/amd-sev-support.service
@@ -0,0 +1,12 @@
+[Unit]
+Description=Read AMD SEV Parameters
+RequiresMountsFor=/run
+Before=pve-ha-lrm.service
+Before=pve-guests.service
+
+[Service]
+ExecStart=/usr/libexec/qemu-server/amd-sev-support
+Type=forking
+
+[Install]
+WantedBy=multi-user.target
-- 
2.39.2



_______________________________________________
pve-devel mailing list
pve-devel@lists.proxmox.com
https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel

[pve-devel] [PATCH qemu-server v5 2/3] config: QEMU AMD SEV enable

[Markus Frank]

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@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



_______________________________________________
pve-devel mailing list
pve-devel@lists.proxmox.com
https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel

[pve-devel] [PATCH docs v5 3/3] add AMD SEV documentation

[Markus Frank]

add documentation for the "[PATCH qemu-server] config: QEMU AMD SEV enable"
patch.

Signed-off-by: Markus Frank <m.frank@proxmox.com>
---
v5:
* removed NodeConfig part

v4:
* added text that SEV-ES is experimental

 qm.adoc | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)

diff --git a/qm.adoc b/qm.adoc
index 45e3a57..6590373 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: <buildversion>
+[...] SEV supported: <number> ASIDs
+[...] SEV-ES supported: <number> 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 <vmid> -amd_sev type=std,nodbg=1,noks=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 *nodbg* and *noks*
+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* is per default off 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
-- 
2.39.2



_______________________________________________
pve-devel mailing list
pve-devel@lists.proxmox.com
https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel