Messages in this thread | | | Date | Tue, 2 Oct 2018 14:13:14 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [tip:x86/hyperv] x86/hyperv: Enable PV qspinlock for Hyper-V |
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On Tue, 2 Oct 2018, Juergen Gross wrote:
> Sorry for noticing this only now, but I have been fighting with > Xen PV qspinlocks last weekend: > > > + /* > > + * Read HV_X64_MSR_GUEST_IDLE MSR can trigger the guest's > > + * transition to the idle power state which can be exited > > + * by an IPI even if IF flag is disabled. > > + */ > > What if interrupts are enabled? Won't a kick happening here just > interrupt and then the following rdmsr result in a hang? > > I believe the correct way would be to: > > - disable interrupts before above READ_ONCE() and restore them > after the rdmsrl() > > - return early if in_nmi() > > similar as the kvm specific variant is doing it.
Interesting question. I zapped the last commit for now until this is clarified.
Thanks,
tglx
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