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Re: [qemu-s390x] [PATCH v1 for-2.12] s390x/kvm: call cpu_synchronize_sta
From: |
Christian Borntraeger |
Subject: |
Re: [qemu-s390x] [PATCH v1 for-2.12] s390x/kvm: call cpu_synchronize_state() on every kvm_arch_handle_exit() |
Date: |
Fri, 6 Apr 2018 12:10:02 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
On 04/06/2018 11:35 AM, David Hildenbrand wrote:
> Manually having to use cpu_synchronize_state() is error prone. And as
> Christian Borntraeger discovered, e.g. handle_diag() is currently
> missing a cpu_synchronize_state(), as decode_basedisp_s() uses a
> general purpose register value internally.
>
> So let's do an overall cpu_synchronize_state(), which fixes at least the
> one mentioned BUG. We will clean up the superfluous cpu_synchronize_state()
> calls later.
>
> We now also call it (although maybe not neded) for
> - KVM_EXIT_S390_RESET -> s390_reipl_request()
> - KVM_EXIT_DEBUG -> kvm_arch_handle_debug_exit()
> - unmanagable/unimplemented intercepts
> - ICPT_CPU_STOP -> do_stop_interrupt() -> cpu gets halted
> - Scenarios where we inject an operation exception
> - handle_stsi()
>
> I don't think any of these are performance critical. Especially as we
> have all information directly contained in kvm_run, there are no
> additional IOCTLs to issue on modern kernels.
>
> Signed-off-by: David Hildenbrand <address@hidden>
Acked-by: Christian Borntraeger <address@hidden>
ok for 2.12.
> ---
> target/s390x/kvm.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index f570896dc1..fb59d92def 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -1778,6 +1778,8 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run
> *run)
>
> qemu_mutex_lock_iothread();
>
> + cpu_synchronize_state(cs);
> +
> switch (run->exit_reason) {
> case KVM_EXIT_S390_SIEIC:
> ret = handle_intercept(cpu);
>