Re: [GIT PULL] First batch of KVM changes for 4.1

Marcelo Tosatti
2015-04-22T20:57:25Z

On Mon, Apr 20, 2015 at 06:59:04PM +0200, Paolo Bonzini wrote:
>
>
> On 17/04/2015 22:18, Marcelo Tosatti wrote:
> > The bug which this is fixing is very rare, have no memory of a report.
> >
> > In fact, its even difficult to create a synthetic reproducer.
>
> But then why was the task migration notifier even in Jeremy's original
> code for Xen?

To cover for the vcpu1 -> vcpu2 -> vcpu1 case, i believe.

> Was it supposed to work even on non-synchronized TSC?

Yes it is supposed to work on non-synchronized TSC.

> If that's the case, then it could be reverted indeed; but then why did
> you commit this patch to 4.1?

Because it fixes the problem Andy reported (see Subject: KVM: x86: fix
kvmclock write race (v2) on kvm@). As long as you have Radim's
fix on top.

> Did you think of something that would
> cause the seqcount-like protocol to fail, and that turned out not to be
> the case later? I was only following the mailing list sparsely in March.

No.