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Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] pseries: fix TCG migration
From: |
Suraj Jitindar Singh |
Subject: |
Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] pseries: fix TCG migration |
Date: |
Wed, 29 Nov 2017 10:58:29 +1100 |
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 :)
Reviewed-by: Suraj Jitindar Singh <address@hidden>
> ---
> v2: fix the comment to keep GDB backtrace lines starting with '#'
>
> hw/ppc/spapr.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 9efddeaee5..a471de6cab 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1570,7 +1570,7 @@ static int spapr_post_load(void *opaque, int
> version_id)
> err = spapr_rtc_import_offset(&spapr->rtc, spapr-
> >rtc_offset);
> }
>
> - if (spapr->patb_entry) {
> + if (kvm_enabled() && spapr->patb_entry) {
> PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> bool radix = !!(spapr->patb_entry & PATBE1_GR);
> bool gtse = !!(cpu->env.spr[SPR_LPCR] & LPCR_GTSE);