Re: [Qemu-ppc] POWER8 <-> POWER8E migration changed/broken in ppc-for.2.10. Intended?

[Thomas Huth]

On 22.06.2017 05:22, Alexey Kardashevskiy wrote:
> On 22/06/17 12:49, Alexey Kardashevskiy wrote:
>> On 22/06/17 11:45, Alexey Kardashevskiy wrote:
>>> On 22/06/17 07:19, Daniel Henrique Barboza wrote:
>>>> Hi,
>>>>
>>>> Yesterday I noticed that the migration between POWER8 and POWER8E hosts
>>>> isn't working
>>>> as before. These are the machines that I've been using for DRC testing and
>>>> I discovered
>>>> this behavior when trying to test the DRC cleanup series (v5).
>>>>
>>>> What happens in that the migration seems to be completed - no errors on
>>>> both source and
>>>> destination, destination status marked as 'running' - but the guest at dest
>>>> looks
>>>> frozen/inactive. Migrating from POWER8 to POWER8E or the other way around
>>>> presents the same behavior.
>>>>
>>>> This is the command line I'm executing:
>>>>
>>>> sudo ./qemu-system-ppc64 -name migrate_qemu -boot strict=on -device
>>>> nec-usb-xhci,id=usb,bus=pci.0,addr=0xf -device
>>>> spapr-vscsi,id=scsi0,reg=0x2000 -smp
>>>> 1,maxcpus=4,sockets=4,cores=1,threads=1 --machine
>>>> pseries,accel=kvm,kvm-type=HV,usb=off,dump-guest-core=off -m
>>>> 4G,slots=32,maxmem=32G -drive
>>>> file=/home/danielhb/vm_imgs/ubuntu1704.qcow2,format=qcow2,if=none,id=drive-virtio-disk0,cache=none
>>>> -device
>>>> virtio-blk-pci,scsi=off,bus=pci.0,addr=0x2,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1
>>>> -nographic
>>>>
>>>> I've tracked the problem down to the commit b0517f54ef7d, "ppc: Rework CPU
>>>> compatibility testing across migration". If I revert this commit, migration
>>>> works as before
>>>> between these hosts.
>>>
>>> With b0517f54ef7d, CPU state is not marked dirty and SPRs (all registers in
>>> fact) are not put to KVM at the end of migration, hence the freeze, this
>>> has something to do with cpu_synchronize_state() called from 
>>> ppc_set_compat().
>>
>> No, I was not right, please ignore.
> 
> 
> This hack fixes it:
> 
> 
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index f2f7c531bc..7ec4146b2b 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -919,6 +919,7 @@ static int kvm_put_vpa(CPUState *cs)
>      return 0;
>  }
>  #endif /* TARGET_PPC64 */
> +static uint32_t mfpvr(void);
> 
>  int kvmppc_put_books_sregs(PowerPCCPU *cpu)
>  {
> @@ -927,7 +928,7 @@ int kvmppc_put_books_sregs(PowerPCCPU *cpu)
>      int i;
> 
>      sregs.pvr = env->spr[SPR_PVR];
> -
> +    sregs.pvr = mfpvr();
>      sregs.u.s.sdr1 = env->spr[SPR_SDR1];
> 
>      /* Sync SLB */

In case you consider to submit this patch: Please add a check for
!kvmppc_is_pr() so that this is only done for KVM-HV.

But I think the right way to hack this is somewhere in machine.c
instead, eg. in cpu_post_load().

 Thomas