Re: [Xen-devel] [PATCH v3.1 10/15] xen/x86: split Dom0 build into PV and PVHv2

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

On Fri, Nov 11, 2016 at 09:53:49AM -0700, Jan Beulich wrote:
> >>> On 29.10.16 at 10:59, <roger.pau@xxxxxxxxxx> wrote:
> > --- a/xen/arch/x86/domain_build.c
> > +++ b/xen/arch/x86/domain_build.c
> > @@ -191,10 +191,8 @@ struct vcpu *__init alloc_dom0_vcpu0(struct domain 
> > *dom0)
> >  }
> >  
> >  #ifdef CONFIG_SHADOW_PAGING
> > -static bool_t __initdata opt_dom0_shadow;
> > +bool __initdata opt_dom0_shadow;
> >  boolean_param("dom0_shadow", opt_dom0_shadow);
> > -#else
> > -#define opt_dom0_shadow 0
> >  #endif
> 
> I think the new option parsing would better go here, avoiding the need
> for this change. Making dom0_hvm visible globally is the less intrusive
> variant.

I'm not sure I follow your point, even if dom0_hvm is defined here together 
with the parsing, opt_dom0_shadow still needs to be made global, so it can be 
accessed from setup.c which is where the domain_create call happens.
 
> > --- a/xen/arch/x86/setup.c
> > +++ b/xen/arch/x86/setup.c
> > @@ -67,6 +67,16 @@ unsigned long __read_mostly cr4_pv32_mask;
> >  static bool_t __initdata opt_dom0pvh;
> >  boolean_param("dom0pvh", opt_dom0pvh);
> >  
> > +/*
> > + * List of parameters that affect Dom0 creation:
> > + *
> > + *  - hvm               Create a PVHv2 Dom0.
> > + *  - shadow            Use shadow paging for Dom0.
> > + */
> > +static void parse_dom0_param(char *s);
> 
> Please try to avoid such forward declarations.
> 
> > @@ -1543,6 +1574,14 @@ void __init noreturn __start_xen(unsigned long mbi_p)
> >      if ( opt_dom0pvh )
> >          domcr_flags |= DOMCRF_pvh | DOMCRF_hap;
> >  
> > +    if ( dom0_hvm )
> > +    {
> > +        domcr_flags |= DOMCRF_hvm |
> > +                       ((hvm_funcs.hap_supported && !opt_dom0_shadow) ?
> > +                         DOMCRF_hap : 0);
> > +        config.emulation_flags = XEN_X86_EMU_LAPIC|XEN_X86_EMU_IOAPIC;
> > +    }
> 
> If you wire this up here already, instead of later in the series, what's
> the effect of someone using this option? Crash?

Most certainly. The BSP IP points to 0 at this point. I can wire this up later, 
but it's going to be strange IMHO.

Roger.

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