From: Yi Sun <yi.y.sun@linux.intel.com>
To: Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
mingo@kernel.org, sthemmin@microsoft.com, mikelley@microsoft.com,
kys@microsoft.com, haiyangz@microsoft.com, hpa@zytor.com
Subject: Re: [tip:x86/hyperv] x86/hyperv: Enable PV qspinlock for Hyper-V
Date: Mon, 8 Oct 2018 16:12:23 +0800 [thread overview]
Message-ID: <20181008081223.GG11769@yi.y.sun> (raw)
In-Reply-To: <0005fc50-4415-87a0-1954-fb15a1f8bd0b@suse.com>
On 18-10-02 13:38:55, Juergen Gross wrote:
> > +static void hv_qlock_wait(u8 *byte, u8 val)
> > +{
> > + unsigned long msr_val;
> > +
> > + if (READ_ONCE(*byte) != val)
> > + return;
> > +
> > + /*
> > + * 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.
>
>
> Juergen
Thank you for the suggestion! That is a possible case. I will submit
a new version in soon.
BRs,
Yi Sun
next prev parent reply other threads:[~2018-10-08 8:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-27 6:01 [PATCH v3 0/2] Enable PV qspinlock for Hyper-V Yi Sun
2018-09-27 6:01 ` [PATCH v3 1/2] X86/Hyper-V: Add Guest IDLE MSR support Yi Sun
2018-10-02 11:27 ` [tip:x86/hyperv] x86/hyperv: Add GUEST_IDLE_MSR support tip-bot for Yi Sun
2018-10-09 12:27 ` [tip:x86/paravirt] " tip-bot for Yi Sun
2018-09-27 6:01 ` [PATCH v3 2/2] locking/pvqspinlock, hv: Enable PV qspinlock for Hyper-V Yi Sun
2018-09-28 22:09 ` Michael Kelley (EOSG)
2018-10-02 11:28 ` [tip:x86/hyperv] x86/hyperv: " tip-bot for Yi Sun
2018-10-02 11:38 ` Juergen Gross
2018-10-02 12:13 ` Thomas Gleixner
2018-10-08 8:12 ` Yi Sun [this message]
-- strict thread matches above, loose matches on Subject: below --
2018-10-08 8:29 [PATCH v4 2/2] locking/pvqspinlock, hv: " Yi Sun
2018-10-09 9:30 ` [tip:x86/hyperv] x86/hyperv: " tip-bot for Yi Sun
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