On 9/30/19 12:58 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.
>
> 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').
mentioning that pvestatd broadcasts this in an intelligent way would be nice
above, else one may wonder how/why that can/should be used.
> +#
> +sub query_supported_cpu_flags {
> + my $flags = [];
> +
> + my $vmid = -1;
maybe 's/vmid/fakevmid/' ? or tempvmid, virtvmid ?
do underline that it's intended that this cannot exists.
> + 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) {
AFAICT, above is not really required, the "for my $prop (%$foo) { }
can handle an empty %$foo
> + 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;
hmm, the assignmend to the same variable and double use in two grep's
is a bit to much for me to understand in contrast of what you want to
achieve ^^
Why not do it in the for my $prop %$pros loop already? maybe using a
hash (internally) could be easier? It's properties helps your cause here.
my $flags = {};
...
for my $prop (keys %$props) {
if ($props->{$prop}) {
# QEMU tells us about the same flag in different way (e.g., sse4.2,
sse4-2
# and sse4_2) just record the underscore separated one, like
/proc/cpuinfo uses
$prop = $prop s/\.|-/_/g;
$flags->{$prop} = 1;
}
}
then you do not need to do anything here anymore and if you want to return
an array you can do:
return [ keys %$flags ];
IMO a bit simpler
> +
> + 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) = @_;
>
>
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