On Thu, 01 Dec 2011, Jan Kiszka wrote:
> On 2011-11-29 22:36, Eric B Munson wrote:
> > Often when a guest is stopped from the qemu console, it will report spurious
> > soft lockup warnings on resume. There are kernel patches being discussed that
> > will give the host the ability to tell the guest that it is being stopped and
> > should ignore the soft lockup warning that generates.
> >
> > Signed-off-by: Eric B Munson <emunson@xxxxxxxxx>
> > Cc: ryanh@xxxxxxxxxxxxxxxxxx
> > Cc: aliguori@xxxxxxxxxx
> > Cc: mtosatti@xxxxxxxxxx
> > Cc: avi@xxxxxxxxxx
> > Cc: kvm@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > ---
> > target-i386/kvm.c | 6 ++++++
> > 1 files changed, 6 insertions(+), 0 deletions(-)
> >
> > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > index 5bfc21f..defd364 100644
> > --- a/target-i386/kvm.c
> > +++ b/target-i386/kvm.c
> > @@ -336,12 +336,18 @@ static int kvm_inject_mce_oldstyle(CPUState *env)
> > return 0;
> > }
> >
> > +static void kvm_put_guest_paused(CPUState *penv)
> > +{
> > + kvm_vcpu_ioctl(penv, KVM_GUEST_PAUSED, 0);
> > +}
>
> I see no need in encapsulating this in a separate function.
>
The encapsulated function was from a previous idea, I will remove it for V2.
> > +
> > static void cpu_update_state(void *opaque, int running, RunState state)
> > {
> > CPUState *env = opaque;
> >
> > if (running) {
> > env->tsc_valid = false;
> > + kvm_put_guest_paused(env);
>
> checkpatch.pl would have asked you to remove this tab.
Will change to spaces for V2.
>
> More general:
>
> Why is this x86-only? If the kernel interface is x86-only, what prevents
> making it generic right from the beginning?
>
> Why do we need a new IOCTL for this? Was there no space left in the
> kvm_run structure e.g. to pass this flag down on next vcpu execution? No
> big deal, just wondering.
Thanks for your review/feedback.
When I started looking into this problem, the ioctl was the first suggestion I
got for how to communicate from qemu to guest kernel. I don't see a technical
reason that this could not be added to the kvm_run structure in one of the
bytes currently used as padding. I would prefer to keep the ioctl because I
have the corresponding kernel patches out to work with this, however, if there
is a strong preference for using kvm_run, I can rework both sets.
Eric
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