RE: [PATCH 1/1] x86/hyper-V: Allocate the IDT entry early in boot

[KY Srinivasan]

> -----Original Message-----
> From: Ingo Molnar [mailto:mingo.kernel.org@xxxxxxxxx] On Behalf Of Ingo
> Molnar
> Sent: Wednesday, September 13, 2017 2:01 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>; x86@xxxxxxxxxx;
> gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx;
> jasowang@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; hpa@xxxxxxxxx
> Subject: Re: [PATCH 1/1] x86/hyper-V: Allocate the IDT entry early in boot
> 
> 
> * KY Srinivasan <kys@xxxxxxxxxxxxx> wrote:
> 
> >
> >
> > > -----Original Message-----
> > > From: Dan Carpenter [mailto:dan.carpenter@xxxxxxxxxx]
> > > Sent: Saturday, September 9, 2017 4:04 AM
> > > To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> > > Cc: x86@xxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; linux-
> > > kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx;
> > > apw@xxxxxxxxxxxxx; jasowang@xxxxxxxxxx; tglx@xxxxxxxxxxxxx;
> > > hpa@xxxxxxxxx; mingo@xxxxxxxxxx
> > > Subject: Re: [PATCH 1/1] x86/hyper-V: Allocate the IDT entry early in boot
> > >
> > > On Fri, Sep 08, 2017 at 04:15:57PM -0700, kys@xxxxxxxxxxxxxxxxxxxxxx
> > > wrote:
> > > > From: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
> > > >
> > > > Allocate the hypervisor callback IDT entry early in the boot sequence.
> > > >
> > >
> > > I'm guessing this fixes a NULL dereference or something?  The changelog
> > > doesn't really say why we are doing this.
> >
> > The changelog does say what we are doing - allocating the IDT entry early in
> the boot sequence.
> 
> But the question was the 'why', not the 'what' - so Dan's question is
> fully justified ...
> 
> > The current code would allocate the entry as part of registering the handler
> > when vmbus driver loaded and this caused a problem for the cleanup
> Thomas had
> > implemented.
> 
> I've put this explanation into the changelog.

You are right. Thanks, Ingo.

K. Y
> 
> Thanks,
> 
> 	Ingo