From ac1cb3cd7c1d9232ce1663e469d519319f4ed812 Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Fri, 17 Oct 2025 04:36:08 -0400
Subject: [PATCH] lib/qemu.c: Add -cpu max when testing for KVM via QMP

On RHEL 10.2 aarch64 (only) we see:

  $ echo '{ "execute": "qmp_capabilities" }' '{ "execute": "query-kvm" }' '{ "execute": "quit" }'  | QEMU_AUDIO_DRV=none "/usr/libexec/qemu-kvm" -display none -machine "virt,accel=kvm:hvf:tcg" -qmp stdio
  qemu-kvm: invalid accelerator hvf
  qemu-kvm: falling back to KVM
  {"QMP": {"version": {"qemu": {"micro": 0, "minor": 1, "major": 9}, "package": "qemu-kvm-9.1.0-15.el10_0.4"}, "capabilities": ["oob"]}}
  qemu-kvm: warning: CPU model cortex-a57-arm-cpu is deprecated -- use 'host' / 'max'
  qemu-kvm: kvm_init_vcpu: kvm_arch_init_vcpu failed (0): Invalid argument

Unfortunately we cannot use guestfs_int_get_cpu_model (as that
requires us to already know if KVM is supported), so we just have to
guess that -cpu max will work, at least enough for QMP to work.

Fixes: https://issues.redhat.com/browse/RHEL-121076
Reported-by: Xiang Hua Chen
---
 lib/qemu.c                | 1 +
 tests/disks/debug-qemu.sh | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/qemu.c b/lib/qemu.c
index 15e729839..b8cc9c5a1 100644
--- a/lib/qemu.c
+++ b/lib/qemu.c
@@ -80,6 +80,7 @@ generic_qmp_test (guestfs_h *g, const char *qmp_command, char **outp)
   guestfs_int_cmd_add_string_unquoted (cmd, "QEMU_AUDIO_DRV=none ");
   guestfs_int_cmd_add_string_quoted (cmd, g->hv);
   guestfs_int_cmd_add_string_unquoted (cmd, " -display none");
+  guestfs_int_cmd_add_string_unquoted (cmd, " -cpu max");
   guestfs_int_cmd_add_string_unquoted (cmd, " -machine ");
   guestfs_int_cmd_add_string_quoted (cmd,
 #ifdef MACHINE_TYPE
diff --git a/tests/disks/debug-qemu.sh b/tests/disks/debug-qemu.sh
index e6e80abe3..96c90553b 100755
--- a/tests/disks/debug-qemu.sh
+++ b/tests/disks/debug-qemu.sh
@@ -25,7 +25,7 @@ fi
 
 # The direct backend runs qemu ... -qmp stdio to query for KVM.  For
 # the test to pass we have to provide an answer here.
-if [ "x$5" = "x-qmp" ]; then
+if [ "x$7" = "x-qmp" ]; then
     # Consume stdin first.
     cat >/dev/null
     # Write some fake output.