On October 15, 2019 4:12 pm, Stefan Reiter wrote:
> * 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.
>
> Note that KVM and TCG accelerators provide different expansions for the
> "host" CPU type, so we need to query both.
>
> Currently only supports x86_64, because QEMU-aarch64 doesn't provide the
> necessary querying functions.
>
> Signed-off-by: Stefan Reiter <[email protected]>
> ---
>
> 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.
>
> v2 -> v3:
> * support tcg accelerator as well as KVM (only query TCG on hosts without KVM)
> * change query_understood_cpu_flags to read the static file generated in 02/11
> * simplify s/\.|-/_/g and dedup code
> * $vmid -> $fakevmid
> * better comments
>
> 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 | 117 +++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 116 insertions(+), 1 deletion(-)
>
> diff --git a/PVE/QemuServer.pm b/PVE/QemuServer.pm
> index 8376260..4447afc 100644
> --- a/PVE/QemuServer.pm
> +++ b/PVE/QemuServer.pm
> @@ -24,7 +24,7 @@ use Storable qw(dclone);
> use MIME::Base64;
> use PVE::Exception qw(raise raise_param_exc);
> use PVE::Storage;
> -use PVE::Tools qw(run_command lock_file lock_file_full file_read_firstline
> dir_glob_foreach $IPV6RE);
> +use PVE::Tools qw(run_command lock_file lock_file_full file_read_firstline
> file_get_contents dir_glob_foreach $IPV6RE);
> use PVE::JSONSchema qw(get_standard_option);
> use PVE::Cluster qw(cfs_register_file cfs_read_file cfs_write_file
> cfs_lock_file);
> use PVE::INotify;
> @@ -3534,6 +3534,121 @@ sub get_command_for_arch($) {
> 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.
> +#
> +# query_supported_ needs to start up to 2 temporary VMs 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').
this comment is now outdated, since pvestatd broadcasts cpuflags-tcg and
cpuflags-kvm
> +#
> +# pvestatd calls this function on startup and whenever the QEMU/KVM version
> +# changes, automatically populating pmxcfs.
> +#
> +# Returns: { kvm => [ flagX, flagY, ... ], tcg => [ flag1, flag2, ... ] }
> +# since kvm and tcg machines support different flags
> +#
> +sub query_supported_cpu_flags {
> + my $flags = {};
> +
> + my ($arch, $default_machine) = get_basic_machine_info();
> +
> + # FIXME: Once this is merged, the code below should work for ARM as well:
> + # 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";
> +
> + my $kvm_supported = defined(kvm_version());
> + my $qemu_cmd = get_command_for_arch($arch);
> + my $fakevmid = -1;
> + my $pidfile = pidfile_name($fakevmid);
> +
> + # Start a temporary (frozen) VM with vmid -1 to allow sending a QMP
> command
> + my $query_supported_run_qemu = sub {
> + my ($kvm) = @_;
> +
> + my $flags = {};
> + my $cmd = [
> + $qemu_cmd,
> + '-machine', $default_machine,
> + '-display', 'none',
> + '-chardev',
> "socket,id=qmp,path=/var/run/qemu-server/$fakevmid.qmp,server,nowait",
> + '-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;
> +
> + eval {
> + my $cmd_result = vm_mon_cmd_nocheck(
> + $fakevmid,
> + 'query-cpu-model-expansion',
> + type => 'full',
> + model => { name => 'host' }
> + );
> +
> + my $props = $cmd_result->{model}->{props};
> + foreach my $prop (keys %$props) {
> + next if $props->{$prop} ne '1';
> + # QEMU returns some flags multiple times, with '_', '.' or '-'
> + # (e.g. lahf_lm and lahf-lm; sse4.2, sse4-2 and sse4_2; ...).
> + # We only keep those with underscores, to match /proc/cpuinfo
> + $prop =~ s/\.|-/_/g;
> + $flags->{$prop} = 1;
> + }
> + };
> + my $err = $@;
> +
> + # force stop with 10 sec timeout and 'nocheck'
> + # always stop, even if QMP failed
> + vm_stop(undef, $fakevmid, 1, 1, 10, 0, 1);
> +
> + die $err if $err;
> +
> + return [ keys %$flags ];
sort keys ? sorting once here seems better than sorting when using it
later ;)
> + };
> +
> + # We need to query QEMU twice, since KVM and TCG have different
> supported flags
> + PVE::QemuConfig->lock_config($fakevmid, sub {
> + $flags->{tcg} = eval { $query_supported_run_qemu->(0) };
> + warn "warning: failed querying supported tcg flags: $@\n" if $@;
> +
> + if ($kvm_supported) {
> + $flags->{kvm} = eval { $query_supported_run_qemu->(1) };
> + warn "warning: failed querying supported kvm flags: $@\n" if $@;
> + }
> + });
> +
> + return $flags;
> +}
> +
> +# Understood CPU flags are written to a file at 'pve-qemu' compile time
> +my $understood_cpu_flag_dir = "/usr/share/kvm";
> +sub query_understood_cpu_flags {
> + my $arch = get_host_arch();
> + my $filepath = "$understood_cpu_flag_dir/cpu-flags-understood-$arch";
> +
> + die "Cannot query understood QEMU CPU flags for architecture: $arch
> (file not found)\n"
> + if ! -e $filepath;
> +
> + my $raw = file_get_contents($filepath);
> + $raw =~ s/^\s+|\s+$//g;
> + my @flags = split(/\s+/, $raw);
> +
> + return \@flags;
> +}
> +
> sub get_cpu_options {
> my ($conf, $arch, $kvm, $machine_type, $kvm_off, $kvmver, $winversion,
> $gpu_passthrough) = @_;
>
> --
> 2.20.1
>
>
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>
>
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