linux-kernel - RE: [PATCH 1/1] x86/platform/hyperv: When on Hyper-v use NULL legacy PIC

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Date:	Fri, 4 Apr 2014 22:53:53 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	Dave Young <dyoung@...hat.com>
Subject: RE: [PATCH 1/1] x86/platform/hyperv: When on Hyper-v use NULL
 legacy PIC



> -----Original Message-----
> From: Vivek Goyal [mailto:vgoyal@...hat.com]
> Sent: Friday, April 4, 2014 1:32 PM
> To: KY Srinivasan
> Cc: x86@...nel.org; linux-kernel@...r.kernel.org; olaf@...fle.de;
> apw@...onical.com; jasowang@...hat.com; hpa@...or.com;
> stable@...r.kernel.org; Dave Young
> Subject: Re: [PATCH 1/1] x86/platform/hyperv: When on Hyper-v use NULL
> legacy PIC
> 
> On Fri, Apr 04, 2014 at 08:09:47PM +0000, KY Srinivasan wrote:
> >
> >
> > > -----Original Message-----
> > > From: Vivek Goyal [mailto:vgoyal@...hat.com]
> > > Sent: Friday, April 4, 2014 8:16 AM
> > > To: KY Srinivasan
> > > Cc: x86@...nel.org; linux-kernel@...r.kernel.org; olaf@...fle.de;
> > > apw@...onical.com; jasowang@...hat.com; hpa@...or.com;
> > > stable@...r.kernel.org; Dave Young
> > > Subject: Re: [PATCH 1/1] x86/platform/hyperv: When on Hyper-v use
> > > NULL legacy PIC
> > >
> > > On Fri, Apr 04, 2014 at 03:01:51PM +0000, KY Srinivasan wrote:
> > >
> > > [..]
> > > > The problem we were having is that the initial boot on the EFI
> > > > firmware would succeed as the legacy PIC would be NULL legacy PIC,
> > > > however in the kexeced kernel, the initial boot information is not
> > > > available and so we would not set the legacy PIC to NULL legacy PIC.
> > >
> > > I am curious to know what "initial boot information" is not
> > > available in kexeced kernel and who is supposed to provide that.
> > >
> > > Is it a bug or that's how it is supposed to work.
> >
> > As the name indicates, the dump kernel is not "booted" but it is kexeced.
> > In the address space of this second kernel, the initial boot state is not
> visible.
> 
> What do you mean by "initial boot state"? Most of the state we pass to
> second kernel in bootparams and on command line and rest second kernel
> can query from firmware as needed.
Specifically, this check I had:
if (efi_enabled(EFI_BOOT)) {
}

Fails in the kexeced kernel even when running on EFI firmware.

K. Y
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