linux-kernel - RE: [PATCH 0/4] x86/Hyper-V: Unload vmbus channel in hv panic callback

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Date:   Thu, 19 Mar 2020 15:06:35 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     vkuznets <vkuznets@...hat.com>,
        "ltykernel@...il.com" <ltykernel@...il.com>
CC:     Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <liuwe@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "hpa@...or.com" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH 0/4] x86/Hyper-V: Unload vmbus channel in hv panic
 callback

From: Vitaly Kuznetsov <vkuznets@...hat.com>  Sent: Thursday, March 19, 2020 1:04 AM
> 
> Michael Kelley <mikelley@...rosoft.com> writes:
> 
> >> > --- a/drivers/hv/vmbus_drv.c
> >> > +++ b/drivers/hv/vmbus_drv.c
> >> > @@ -53,9 +53,12 @@ static int hyperv_panic_event(struct notifier_block *nb,
> unsigned
> >> long val,
> >> >  {
> >> >  	struct pt_regs *regs;
> >> >
> >> > -	regs = current_pt_regs();
> >> > +	vmbus_initiate_unload(true);
> >> >
> >> > -	hyperv_report_panic(regs, val);
> >> > +	if (ms_hyperv.misc_features & HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE) {
> >>
> >> With Michael's effors to make code in drivers/hv arch agnostic, I think
> >> we need a better, arch-neutral way.
> >
> > Vitaly -- could you elaborate on what part is not arch-neutral?  I don't see
> > a problem.  ms_hyperv and the misc_features field exist for both the x86
> > and ARM64 code branches.  It turns out the particular bit for
> > GUEST_CRASH_MSR_AVAILABLE is different on the two architectures, but
> > the compiler will do the right thing.
> >
> 
> Ah, apologies, missed the fact that we also call it
> 'HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE' - I have to admit I was confused
> by the 'MSR' part. We can probably rename this to something like
> HV_FEATURE_GUEST_CRASH_REGS_AVAILABLE - but not as part of the series.
> 

Good point.  Agreed.

Michael