Re: [PATCH v2 1/2] target/arm: kvm: Inject events at the last stage of sync

[Beata Michalska <beata.michalska@linaro.org>]

On Tue, 4 Feb 2020 at 10:34, Andrew Jones <drjones@redhat.com> wrote:
>
> On Wed, Jan 29, 2020 at 08:24:40PM +0000, Beata Michalska wrote:
> > KVM_SET_VCPU_EVENTS might actually lead to vcpu registers being modified.
> > As such this should be the last step of sync to avoid potential overwriting
> > of whatever changes KVM might have done.
> >
> > Signed-off-by: Beata Michalska <beata.michalska@linaro.org>
> > ---
> >  target/arm/kvm32.c | 20 ++++++++++----------
> >  target/arm/kvm64.c | 20 ++++++++++----------
> >  2 files changed, 20 insertions(+), 20 deletions(-)
> >
> > diff --git a/target/arm/kvm32.c b/target/arm/kvm32.c
> > index 32bf8d6..cf2b47f 100644
> > --- a/target/arm/kvm32.c
> > +++ b/target/arm/kvm32.c
> > @@ -386,17 +386,17 @@ int kvm_arch_put_registers(CPUState *cs, int level)
> >          return ret;
> >      }
> >
> > -    ret = kvm_put_vcpu_events(cpu);
> > -    if (ret) {
> > -        return ret;
> > -    }
> > -
> >      write_cpustate_to_list(cpu, true);
> >
> >      if (!write_list_to_kvmstate(cpu, level)) {
> >          return EINVAL;
> >      }
> >
> > +    ret = kvm_put_vcpu_events(cpu);
> > +    if (ret) {
> > +        return ret;
> > +    }
> > +
>
> I think we should put a comment above this that says basically the same
> thing as the commit message in order to explain why kvm_put_vcpu_events()
> *must* be after write_list_to_kvmstate().
>
Will do that.

> >      kvm_arm_sync_mpstate_to_kvm(cpu);
> >
> >      return ret;
> > @@ -462,11 +462,6 @@ int kvm_arch_get_registers(CPUState *cs)
> >      }
> >      vfp_set_fpscr(env, fpscr);
> >
> > -    ret = kvm_get_vcpu_events(cpu);
> > -    if (ret) {
> > -        return ret;
> > -    }
> > -
> >      if (!write_kvmstate_to_list(cpu)) {
> >          return EINVAL;
> >      }
> > @@ -475,6 +470,11 @@ int kvm_arch_get_registers(CPUState *cs)
> >       */
> >      write_list_to_cpustate(cpu);
> >
> > +    ret = kvm_get_vcpu_events(cpu);
> > +    if (ret) {
> > +        return ret;
> > +    }
> > +
>
> Why are we moving kvm_get_vcpu_events()?

This is only to make things consistent with put_registeres.
There is no functional change per se.

BR

Beata

> >      kvm_arm_sync_mpstate_to_qemu(cpu);
> >
> >      return 0;
> > diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
> > index 6344113..d06fd32 100644
> > --- a/target/arm/kvm64.c
> > +++ b/target/arm/kvm64.c
> > @@ -1043,17 +1043,17 @@ int kvm_arch_put_registers(CPUState *cs, int level)
> >          return ret;
> >      }
> >
> > -    ret = kvm_put_vcpu_events(cpu);
> > -    if (ret) {
> > -        return ret;
> > -    }
> > -
> >      write_cpustate_to_list(cpu, true);
> >
> >      if (!write_list_to_kvmstate(cpu, level)) {
> >          return -EINVAL;
> >      }
> >
> > +    ret = kvm_put_vcpu_events(cpu);
> > +    if (ret) {
> > +        return ret;
> > +    }
> > +
> >      kvm_arm_sync_mpstate_to_kvm(cpu);
> >
> >      return ret;
> > @@ -1251,11 +1251,6 @@ int kvm_arch_get_registers(CPUState *cs)
> >      }
> >      vfp_set_fpcr(env, fpr);
> >
> > -    ret = kvm_get_vcpu_events(cpu);
> > -    if (ret) {
> > -        return ret;
> > -    }
> > -
> >      if (!write_kvmstate_to_list(cpu)) {
> >          return -EINVAL;
> >      }
> > @@ -1264,6 +1259,11 @@ int kvm_arch_get_registers(CPUState *cs)
> >       */
> >      write_list_to_cpustate(cpu);
> >
> > +    ret = kvm_get_vcpu_events(cpu);
> > +    if (ret) {
> > +        return ret;
> > +    }
> > +
> >      kvm_arm_sync_mpstate_to_qemu(cpu);
> >
> >      /* TODO: other registers */
> > --
> > 2.7.4
> >
> >
>
> Same comments for kvm64.c as for kvm32.c
>
> Thanks,
> drew
>