On Thu, Feb 24, 2022 at 03:58:16PM -0300, Fabiano Rosas wrote: > When saving the guest "timebase" we look to the first_cpu for its > tb_offset. If that CPU happens to be running a nested guest at this > time, the tb_offset will have the nested guest value. > > This was caught by code inspection.
This doesn't seem right. Isn't the real problem that nested_tb_offset
isn't being migrated? If you migrate that, shouldn't everything be
fixed up when the L1 cpu leaves the nested guest on the destination
host?
>
> Signed-off-by: Fabiano Rosas <faro...@linux.ibm.com>
> ---
> hw/ppc/ppc.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
> index 9e99625ea9..093cd87014 100644
> --- a/hw/ppc/ppc.c
> +++ b/hw/ppc/ppc.c
> @@ -36,6 +36,7 @@
> #include "kvm_ppc.h"
> #include "migration/vmstate.h"
> #include "trace.h"
> +#include "hw/ppc/spapr_cpu_core.h"
>
> static void cpu_ppc_tb_stop (CPUPPCState *env);
> static void cpu_ppc_tb_start (CPUPPCState *env);
> @@ -961,19 +962,33 @@ static void timebase_save(PPCTimebase *tb)
> {
> uint64_t ticks = cpu_get_host_ticks();
> PowerPCCPU *first_ppc_cpu = POWERPC_CPU(first_cpu);
> + int64_t tb_offset;
>
> if (!first_ppc_cpu->env.tb_env) {
> error_report("No timebase object");
> return;
> }
>
> + tb_offset = first_ppc_cpu->env.tb_env->tb_offset;
> +
> + if (first_ppc_cpu->vhyp && vhyp_cpu_in_nested(first_ppc_cpu)) {
> + SpaprCpuState *spapr_cpu = spapr_cpu_state(first_ppc_cpu);
> +
> + /*
> + * If the first_cpu happens to be running a nested guest at
> + * this time, tb_env->tb_offset will contain the nested guest
> + * offset.
> + */
> + tb_offset -= spapr_cpu->nested_tb_offset;
> + }
> +
> /* not used anymore, we keep it for compatibility */
> tb->time_of_the_day_ns = qemu_clock_get_ns(QEMU_CLOCK_HOST);
> /*
> * tb_offset is only expected to be changed by QEMU so
> * there is no need to update it from KVM here
> */
> - tb->guest_timebase = ticks + first_ppc_cpu->env.tb_env->tb_offset;
> + tb->guest_timebase = ticks + tb_offset;
>
> tb->runstate_paused =
> runstate_check(RUN_STATE_PAUSED) ||
> runstate_check(RUN_STATE_SAVE_VM);
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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