Re: [Qemu-ppc] [PATCH v2] pseries: fix TCG migration

[Bharata B Rao]

On Wed, Nov 29, 2017 at 10:58:29AM +1100, Suraj Jitindar Singh wrote:
> On Tue, 2017-11-28 at 18:43 +0100, Laurent Vivier wrote:
> > Migration of pseries is broken with TCG because
> > QEMU tries to restore KVM MMU state unconditionally.
> > 
> > The result is a SIGSEGV in kvm_vm_ioctl():
> > 
> >   #0  kvm_vm_ioctl (s=0x0, type=-2146390353)
> >       at qemu/accel/kvm/kvm-all.c:2032
> >   #1  0x00000001003e3e2c in kvmppc_configure_v3_mmu (cpu=<optimized
> > out>,
> >       radix=<optimized out>, gtse=<optimized out>,
> > proc_tbl=<optimized out>)
> >       at qemu/target/ppc/kvm.c:396
> >   #2  0x00000001002f8b88 in spapr_post_load (opaque=0x1019103c0,
> >       version_id=<optimized out>) at qemu/hw/ppc/spapr.c:1578
> >   #3  0x000000010059e4cc in vmstate_load_state (f=0x106230000,
> >       vmsd=0x1009479e0 <vmstate_spapr>, opaque=0x1019103c0,
> >       version_id=<optimized out>) at qemu/migration/vmstate.c:165
> >   #4  0x00000001005987e0 in vmstate_load (f=<optimized out>,
> > se=<optimized out>)
> >       at qemu/migration/savevm.c:748
> > 
> > This patch fixes the problem by not calling the KVM function with the
> > TCG mode.
> > 
> > Fixes: d39c90f5f3 ("spapr: Fix migration of Radix guests")
> > Signed-off-by: Laurent Vivier <address@hidden>
> 
> Ah, guess I never hit this because I never tested tcg migration with a
> qemu compiled on a kvm enabled system. Nice catch :)

Same here. In fact I had the kvm_enabled() check in the initial verions
but removed later as kvmppc_configure_v3_mmu() was defined separately
as nop for !CONFIG_KVM. But obviously the above combination wasn't covered.

Regards,
Bharata.