Re: [Xen-devel] [PATCH RFC v1 23/74] x86/entry: Probe for Xen early during boot

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Jan 05, 2018 at 06:40:29AM -0700, Jan Beulich wrote:
> >>> On 04.01.18 at 14:05, <wei.liu2@xxxxxxxxxx> wrote:
> > --- /dev/null
> > +++ b/xen/arch/x86/guest/xen.c
> > @@ -0,0 +1,75 @@
> > +/******************************************************************************
> > + * arch/x86/guest/xen.c
> > + *
> > + * Support for detecting and running under Xen.
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; either version 2 of the License, or
> > + * (at your option) any later version.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; If not, see <http://www.gnu.org/licenses/>.
> > + *
> > + * Copyright (c) 2017 Citrix Systems Ltd.
> > + */
> > +#include <xen/init.h>
> > +#include <xen/types.h>
> > +
> > +#include <asm/guest.h>
> > +#include <asm/processor.h>
> > +
> > +#include <public/arch-x86/cpuid.h>
> > +
> > +bool xen_guest;
> 
> __read_mostly?
> 
> > +static uint32_t xen_cpuid_base;
> 
> Depending on future use, __initdata or __read_mostly?
> 
> > --- a/xen/include/asm-x86/guest.h
> > +++ b/xen/include/asm-x86/guest.h
> > @@ -20,6 +20,7 @@
> >  #define __X86_GUEST_H__
> >  
> >  #include <asm/guest/pvh-boot.h>
> > +#include <asm/guest/xen.h>
> >  
> >  #endif /* __X86_GUEST_H__ */
> 
> I'm increasingly curious to understand what this header's purpose
> is meant to be. It looks as if you mean source files to only ever
> include this one, but why? Rather than exposing everything at

Yes there will be file that only includes this header -- the PV in HVM
work doesn't need the PVH bits.

Wei.

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