Choose -cpu max by default

You must set -cpu to something on RHEL 10 with TCG since the kernel on
that platform now requires x86_64-v3.  Choosing a good default is
difficult.  Use -cpu max as that was supposed to fix this, although in
practice it doesn't work very reliably.

This is likely a temporary solution.  More reliable/permanent
solutions include:

 - Allowing the user to set the default CPU at configure time.

 - A large case statement that tries to get it right for every
   possible combination of platform/architecture/KVM/...

 - Fixing -cpu max in qemu

diff --git a/src/qemu-sanity-check.in b/src/qemu-sanity-check.in
index 0c96485..d8962d4 100644 (file)
--- a/src/qemu-sanity-check.in
+++ b/src/qemu-sanity-check.in
@@ -28,18 +28,16 @@ canonical_arch="$(uname -m | sed 's/i[456]86/i386/')"
 verbose=no
 timeout=10m
 accel=kvm:tcg
-cpu=
 memory=768
 console=ttyS0
 machine=
 
-# Both libguestfs and virt-manager choose cpu=host when we think that
-# KVM is available, and default otherwise.  Although testing for KVM
-# is hairy, I found that on aarch64 it can fail unless we choose
-# cpu=host for KVM.
-if test -r /dev/kvm; then
-    cpu=host
-fi
+# Choosing a good CPU default is a minefield.  Ideally '-cpu max' is
+# supposed to choose the best CPU type, but it notably fails on RISC-V
+# (not supported) and x86_64+TCG (enables LA57 which TCG does not
+# emulate).  Default minimum CPU will not work on RHEL 10, since that
+# requires at least x86_64-v3.
+cpu=max
 
 # Default machine and CPU type depends on arch.  You can override this
 # using -m|--machine and --cpu options.
@@ -49,7 +47,6 @@ case "$canonical_arch" in
        machine=virt ;;
     aarch*)
        console=ttyAMA0
-       if [ "$cpu" = "" ]; then cpu=cortex-a57; fi
        machine=virt ;;
     s390*)
        console=ttysclp0 ;;