* query_understood_cpu_flags returns all flags that QEMU/KVM knows about
* query_supported_cpu_flags returns all flags that QEMU/KVM can use on
this particular host.
To get supported flags, a temporary VM is started with QEMU, so we can
issue the "query-cpu-model-expansion" QMP command. This is how libvirt
queries supported flags for its "host-passthrough" CPU type.
query_supported_cpu_flags is thus rather slow and shouldn't be called
unnecessarily.
Currently only supports x86_64, because QEMU-aarch64 doesn't provide the
necessary querying functions.
Signed-off-by: Stefan Reiter <s.rei...@proxmox.com>
---
query_understood_cpu_flags is currently not used, but will be very useful for
the later UI part. I think it thematically fits best with this patch though.
v1 -> v2:
* Change order of functions and add a single, more useful comment on usage
* Do s/\.|-/_/g directly in query_understood_cpu_flags, since the other format
is useless anyway
* Add "die" and FIXME for aarch64, since it doesn't support querying atm
(still, use get_host_arch()/get_basic_machine_info() for now, so once QEMU
supports it, we theoretically just have to remove the "die")
* Do QMP in extra eval, so we don't die before calling vm_stop
PVE/QemuServer.pm | 112 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 112 insertions(+)
diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
index 70ed910..20c1061 100644
--- a/PVE/QemuServer.pm
+++ b/PVE/QemuServer.pm
@@ -3531,6 +3531,118 @@ sub get_command_for_arch($) {
return $cmd;
}
+# To use query_supported_cpu_flags and query_understood_cpu_flags to get flags
+# to use in a QEMU command line (-cpu element), first array_intersect the
result
+# of query_supported_ with query_understood_. This is necessary because:
+#
+# a) query_understood_ returns flags the host cannot use and
+# b) query_supported_ (rather the QMP call) doesn't actually return CPU
+# flags, but CPU settings - with most of them being flags. Those settings
+# (and some flags, curiously) cannot be specified as a "-cpu" argument
+# however.
+#
+# query_supported_ needs to start a temporary VM and is therefore rather
+# expensive. If you need the value returned from this, you can get it much
+# cheaper from pmxcfs using PVE::Cluster::get_node_kv('cpuflags').
+#
+sub query_supported_cpu_flags {
+ my $flags = [];
+
+ my $vmid = -1;
+ my $pidfile = pidfile_name($vmid);
+
+ my ($arch, $default_machine) = get_basic_machine_info();
+
+ # FIXME: Once this is merged, the code below should work for ARM without
any
+ # further modifications:
+ # https://lists.nongnu.org/archive/html/qemu-devel/2019-06/msg04947.html
+ die "QEMU/KVM cannot detect CPU flags on ARM (aarch64)\n" if
+ $arch eq "aarch64";
+
+ PVE::QemuConfig->lock_config($vmid, sub {
+ # We start a temporary (frozen) VM with vmid -1 to allow us to send a
QMP command
+ my $rc = run_command([
+ get_command_for_arch($arch),
+ '-machine', $default_machine,
+ '-display', 'none',
+ '-chardev',
"socket,id=qmp,path=/var/run/qemu-server/$vmid.qmp,server,nowait",
+ '-mon', 'chardev=qmp,mode=control',
+ '-pidfile', $pidfile,
+ '-S', '-daemonize'
+ ], noerr => 1, quiet => 0);
+ return if $rc;
+
+ eval {
+ my $cmd_result = vm_mon_cmd_nocheck(
+ $vmid,
+ 'query-cpu-model-expansion',
+ type => 'full',
+ model => { name => 'host' }
+ );
+
+ my $props = $cmd_result->{model}->{props};
+ if (%$props) {
+ foreach my $prop (keys %$props) {
+ push @$flags, $prop if "$props->{$prop}" eq '1';
+ }
+ }
+ };
+ my $err = $@;
+
+ # force stop with 10 sec timeout and 'nocheck'
+ # always stop, even if QMP failed
+ vm_stop(undef, $vmid, 1, 1, 10, 0, 1);
+
+ die $err if $err;
+ });
+
+ # QEMU returns some flags multiple times, with '_', '.' or '-' as separator
+ # (e.g. lahf_lm and lahf-lm; sse4.2, sse4-2 and sse4_2; ...).
+ # We only keep those with underscores, since they match the ones from
+ # /proc/cpuinfo (they do the same thing, but we get rid of duplicates).
+ @$flags = grep {
+ my $replaced = (my $underscore = $_) =~ s/\.|-/_/g;
+ !($replaced && grep { $_ eq $underscore } @$flags)
+ } @$flags;
+
+ return $flags;
+}
+
+sub query_understood_cpu_flags {
+ my $flags = [];
+ my $flag_section = 0;
+
+ my $arch = get_host_arch();
+
+ # FIXME: Once the patch mentioned in query_supported_cpu_flags is merged,
+ # depending on if the ARM version of query-cpu-model-expansion also returns
+ # non-flags, this function might become irrelevant for ARM entirely.
+ die "CPU Flag detection only supported on x86_64\n"
+ if $arch ne "x86_64";
+
+ run_command(
+ [get_command_for_arch($arch), '-cpu', 'help'],
+ noerr => 1,
+ quiet => 1,
+ outfunc => sub {
+ my ($line) = @_;
+
+ if ($flag_section) {
+ return if $line =~ m/^\s*$/;
+ $line =~ s/^\s*|\s*$//g;
+ # Convert all flags to underscore format, since that's what
+ # /proc/cpuinfo and query_supported_cpu_flags use
+ $line =~ s/\.|-/_/g;
+ push @$flags, split(/\s+/, $line);
+ } elsif ($line =~ m/^\s*Recognized CPUID flags:\s*$/) {
+ $flag_section = 1;
+ }
+ }
+ );
+
+ return $flags;
+}
+
sub get_cpu_options {
my ($conf, $arch, $kvm, $machine_type, $kvm_off, $kvmver, $winversion,
$gpu_passthrough) = @_;
--
2.20.1
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