[pve-devel] [PATCH-SERIES qemu-server 0/3] query cpu flags: support aarch64 host

[pve-devel] [PATCH-SERIES qemu-server 0/3] query cpu flags: support aarch64 host

[Fiona Ebner]

Some slight adaptations were necessary. The result on x86_64 should
not change because of those.

qemu-server:

Fiona Ebner (3):
  query cpu flags: fix detecting KVM support
  query cpu flags: query correct model for TCG
  query cpu flags: support aarch64 host

 src/PVE/QemuServer.pm | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)


Summary over all repositories:
  1 files changed, 6 insertions(+), 8 deletions(-)

-- 
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[pve-devel] [PATCH qemu-server 1/3] query cpu flags: fix detecting KVM support

[Fiona Ebner]

KVM can only be used when the host arch matches the vCPU arch.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 src/PVE/QemuServer.pm | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index 7a0a2606..ebb6ae19 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -2939,7 +2939,8 @@ sub vga_conf_has_spice {
 sub query_supported_cpu_flags {
     my ($arch) = @_;
 
-    $arch //= get_host_arch();
+    my $host_arch = get_host_arch();
+    $arch //= $host_arch;
     my $default_machine = PVE::QemuServer::Machine::default_machine_for_arch($arch);
 
     my $flags = {};
@@ -2949,7 +2950,7 @@ sub query_supported_cpu_flags {
     die "QEMU/KVM cannot detect CPU flags on ARM (aarch64)\n"
         if $arch eq "aarch64";
 
-    my $kvm_supported = defined(kvm_version());
+    my $kvm_supported = defined(kvm_version()) && $arch eq $host_arch;
     my $qemu_cmd = PVE::QemuServer::Helpers::get_command_for_arch($arch);
     my $fakevmid = -1;
     my $pidfile = PVE::QemuServer::Helpers::vm_pidfile_name($fakevmid);
-- 
2.47.3



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[pve-devel] [PATCH qemu-server 2/3] query cpu flags: query correct model for TCG

[Fiona Ebner]

With TCG, there is no 'host' model. Use the 'max' model instead. Note
that this does not actually change the result on x86_64 but is
required for aarch64.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 src/PVE/QemuServer.pm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index ebb6ae19..9ab25c49 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -2988,7 +2988,7 @@ sub query_supported_cpu_flags {
                 $fakevmid,
                 'query-cpu-model-expansion',
                 type => 'full',
-                model => { name => 'host' },
+                model => { name => $kvm ? 'host' : 'max' },
             );
 
             my $props = $cmd_result->{model}->{props};
-- 
2.47.3



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[pve-devel] [PATCH qemu-server 3/3] query cpu flags: support aarch64 host

[Fiona Ebner]

Note that for ARM, the 'host' model can only be queried when it is
also used on the commandline. This doesn't change the result for x86_64
either.

The mentioned commit for ARM in the FIXME has long been merged in QEMU
as e19afd5667 ("target/arm/monitor: Introduce
qmp_query_cpu_model_expansion").

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 src/PVE/QemuServer.pm | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index 9ab25c49..1b49e9fd 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -2945,11 +2945,6 @@ sub query_supported_cpu_flags {
 
     my $flags = {};
 
-    # 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()) && $arch eq $host_arch;
     my $qemu_cmd = PVE::QemuServer::Helpers::get_command_for_arch($arch);
     my $fakevmid = -1;
@@ -2978,6 +2973,8 @@ sub query_supported_cpu_flags {
 
         if (!$kvm) {
             push @$cmd, '-accel', 'tcg';
+        } else {
+            push @$cmd, '-cpu', 'host';
         }
 
         my $rc = run_command($cmd, noerr => 1, quiet => 0);
-- 
2.47.3



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Re: [pve-devel] [PATCH-SERIES qemu-server 0/3] query cpu flags: support aarch64 host

[Fiona Ebner]

Am 27.01.26 um 5:15 PM schrieb Fiona Ebner:
> Some slight adaptations were necessary. The result on x86_64 should
> not change because of those.
> 
> qemu-server:
> 
> Fiona Ebner (3):
>   query cpu flags: fix detecting KVM support
>   query cpu flags: query correct model for TCG
>   query cpu flags: support aarch64 host
> 
>  src/PVE/QemuServer.pm | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> 
> Summary over all repositories:
>   1 files changed, 6 insertions(+), 8 deletions(-)
> 

Ping

applied: [pve-devel] [PATCH-SERIES qemu-server 0/3] query cpu flags: support aarch64 host

[Thomas Lamprecht]

On Tue, 27 Jan 2026 17:14:58 +0100, Fiona Ebner wrote:
> Some slight adaptations were necessary. The result on x86_64 should
> not change because of those.
> 
> qemu-server:
> 
> Fiona Ebner (3):
>   query cpu flags: fix detecting KVM support
>   query cpu flags: query correct model for TCG
>   query cpu flags: support aarch64 host
> 
> [...]

Applied, thanks!

[1/3] query cpu flags: fix detecting KVM support
      commit: c506b6ac15683cd0466af73927af9962efcb930d
[2/3] query cpu flags: query correct model for TCG
      commit: 4c765ed36786335071f6dd4467c11f7c5178bd66
[3/3] query cpu flags: support aarch64 host
      commit: 6e4d3a96fcb99ab173b45e735fa7f8a51ba42d9c