linux-kernel - RE: [PATCH 3/4] Drivers: hv: vmbus: Add hooks for per-CPU IRQ

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Message-ID: <CY4PR21MB0773AFA3555BC08A4CC129D4D7D70@CY4PR21MB0773.namprd21.prod.outlook.com>
Date:   Mon, 26 Nov 2018 20:56:50 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     KY Srinivasan <kys@...rosoft.com>,
        "will.deacon@....com" <will.deacon@....com>,
        "catalin.marinas@...m.com" <catalin.marinas@...m.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        vkuznets <vkuznets@...hat.com>
Subject: RE: [PATCH 3/4] Drivers: hv: vmbus: Add hooks for per-CPU IRQ

From: Greg KH <gregkh@...uxfoundation.org>  Monday, November 26, 2018 11:57 AM

> > > You created "null" hooks that do nothing, for no one in this patch
> > > series, why?
> > >
> >
> > hv_enable_vmbus_irq() and hv_disable_vmbus_irq() have non-null
> > implementations in the ARM64 code in patch 2 of this series.  The
> > implementations are in the new file arch/arm64/hyperv/mshyperv.c.
> > Or am I misunderstanding your point?
> 
> So you use a hook in an earlier patch and then add it in a later one?
> 
> Shouldn't you do it the other way around?  As it is, the earlier patch
> should not work properly, right?

The earlier patch implements the hook on the ARM64 side but it is
unused -- it's not called.  The later patch then calls it.  Wouldn't the
other way around be backwards?

The general approach is for patches 1 and 2 of the series to provide
all the new code under arch/arm64 to enable Hyper-V.  But the code
won't get called (or even built) with just these two patches because
CONFIG_HYPERV can't be selected.  Patch 3 is separate because it
applies to architecture independent code and arch/x86 code -- I thought
there might be value in keeping the ARM64 and x86 patches distinct. 
Patch 4 applies to architecture independent code, and enables the
ARM64 code in patches 1 and 2 to be compiled and run when
CONFIG_HYPERV is selected.

If combining some of the patches in the series is a better approach, I'm
good with that.

Michael