linux-kernel - RE: [PATCH v2 char-misc 1/1] x86/hyperv: Add interrupt handler annotations

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Date:   Wed, 4 Apr 2018 15:47:03 +0000
From:   "Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "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>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "leann.ogasawara@...onical.com" <leann.ogasawara@...onical.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>
Subject: RE: [PATCH v2 char-misc 1/1] x86/hyperv: Add interrupt handler
 annotations

> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: Wednesday, April 4, 2018 1:16 AM
> To: Michael Kelley (EOSG) <Michael.H.Kelley@...rosoft.com>
> Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org; olaf@...fle.de;
> apw@...onical.com; vkuznets@...hat.com; jasowang@...hat.com;
> leann.ogasawara@...onical.com; marcelo.cerri@...onical.com; Stephen Hemminger
> <sthemmin@...rosoft.com>; KY Srinivasan <kys@...rosoft.com>
> Subject: Re: [PATCH v2 char-misc 1/1] x86/hyperv: Add interrupt handler annotations
> 
> On Tue, Apr 03, 2018 at 01:59:08PM -0700, mhkelley58@...il.com wrote:
> > From: Michael Kelley <mikelley@...rosoft.com>
> >
> > Add standard interrupt handler annotations to
> > hyperv_vector_handler().
> >
> > Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> > ---
> > Changes in v2:
> > * Fixed From: line
> > ---
> >  arch/x86/kernel/cpu/mshyperv.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index 4488cf0..20f6849 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -41,7 +41,7 @@ static void (*hv_stimer0_handler)(void);
> >  static void (*hv_kexec_handler)(void);
> >  static void (*hv_crash_handler)(struct pt_regs *regs);
> >
> > -void hyperv_vector_handler(struct pt_regs *regs)
> > +__visible void __irq_entry hyperv_vector_handler(struct pt_regs *regs)
> 
> What bug does this solve?  What is wrong with the existing markings?
> What does __visible and __irq_entry give us that we don't already have
> and we need?
> 
> Are you really using LTO that requires this marking to prevent the code
> from being removed?

Thomas Gleixner commented on Vitaly Kuznetsov's Hyper-V reenlightenment patch
that the interrupt handler should have these annotations: see
https://lkml.org/lkml/2018/1/14/145

I put the same annotations on the interrupt handler for stimer0 Direct Mode,
So this change makes the hyperv_vector_handler() consistent with
hv_stimer0_vector_handler() in the same source file.  It does not fix any
immediate bug -- it's for consistency and alignment with what is apparently
standard practice.

Not sure what LTO is ...

Michael

> 
> thanks,
> 
> greg k-h