Re: Windows fails to boot after rebase to QEMU master

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, May 21, 2021 at 11:17:19AM +0200, Siddharth Chandrasekaran wrote:
> After a rebase to QEMU master, I am having trouble booting windows VMs.
> Git bisect indicates commit f5cc5a5c1686 ("i386: split cpu accelerators
> from cpu.c, using AccelCPUClass") to have introduced the issue. I spent
> some time looking at into it yesterday without much luck.
> 
> Steps to reproduce:
> 
>     $ ./configure --enable-kvm --disable-xen --target-list=x86_64-softmmu --enable-debug
>     $ make -j `nproc`
>     $ ./build/x86_64-softmmu/qemu-system-x86_64 \
>         -cpu host,hv_synic,hv_vpindex,hv_time,hv_runtime,hv_stimer,hv_crash \
>         -enable-kvm \
>         -name test,debug-threads=on \
>         -smp 1,threads=1,cores=1,sockets=1 \
>         -m 4G \
>         -net nic -net user \
>         -boot d,menu=on \
>         -usbdevice tablet \
>         -vnc :3 \
>         -machine q35,smm=on \
>         -drive if=pflash,format=raw,readonly=on,unit=0,file="../OVMF_CODE.secboot.fd" \
>         -drive if=pflash,format=raw,unit=1,file="../OVMF_VARS.secboot.fd" \
>         -global ICH9-LPC.disable_s3=1 \
>         -global driver=cfi.pflash01,property=secure,value=on \
>         -cdrom "../Windows_Server_2016_14393.ISO" \
>         -drive file="../win_server_2016.qcow2",format=qcow2,if=none,id=rootfs_drive \
>         -device ahci,id=ahci \
>         -device ide-hd,drive=rootfs_drive,bus=ahci.0
> 
> If the issue is not obvious, I'd like some pointers on how to go about
> fixing this issue.
> 
> ~ Sid.
> 

At a guess this commit inadvertently changed something in the CPU ID.
I'd start by using a linux guest to dump cpuid before and after the
change.


> 
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