RE: [PATCH char-misc 1/1] Drivers: hv: vmbus: Make synic_initialized flag per-cpu

From: Michael Kelley (EOSG)
Date: Tue Aug 28 2018 - 16:20:25 EST

From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Sent: Wednesday, August 1, 2018 2:26 AM

> > I was trying to decide if there are any arguments in favor of one
> > approach vs. the other: a per-cpu flag in memory or checking
> > the synic_control "enable" bit. Seems like a wash to me, in which
> > case I have a slight preference for the per-cpu flag in memory vs.
> > creating another function to return sctrl.enable. But I'm completely
> > open to reasons why checking sctrl.enable is better.
> Just a few thoughts: reading MSR is definitely slower but we avoid
> 'shadowing' the state, the reading is always correct. In case there's a
> chance the SynIC will get disabled from host side we can only find this
> out by doing MSR read. This is a purely theoretical possibility, I
> believe, we can go ahead with this patch.

Vitaly -- just to confirm: you are OK with the patch as is? (I'll
check, but I may need to rebase on the latest code.)