Re: [PATCH RFC] pvh: clearly specify used parameters in vcpu_guest_context

[George Dunlap <george.dunlap@eu.citrix.com>]

On 15/11/13 16:32, Jan Beulich wrote:
>>>> On 15.11.13 at 16:50, Roger Pau Monne <roger.pau@citrix.com> wrote:
>> --- a/xen/arch/x86/domain.c
>> +++ b/xen/arch/x86/domain.c
>> @@ -704,9 +704,11 @@ int arch_set_info_guest(
>>           /* PVH 32bitfixme */
>>           ASSERT(!compat);
>>   
>> -        if ( c(ctrlreg[1]) || c(ldt_base) || c(ldt_ents) ||
>> +        if ( c(ctrlreg[0]) || c(ctrlreg[1]) || c(ctrlreg[2]) ||
>> +             c(ctrlreg[4]) || c(ldt_base) || c(ldt_ents) ||
> I think it should actually be a bug for the guest to request an
> all blank CR0 or CR4. Minimally CR0.PE, CR0.PG, and CR4.PAE
> would seem to be a valid requirement to be set.
>
> Apart from that ctrlreg[] is an 8-element array... And I don't
> see debugreg[] being verified at all.
>
>>                c(user_regs.cs) || c(user_regs.ss) || c(user_regs.es) ||
>>                c(user_regs.ds) || c(user_regs.fs) || c(user_regs.gs) ||
>> +             c(kernel_ss) || c(kernel_sp) || c.nat->gs_base_kernel ||
> So George and/or Mukesh found it necessary to set
> gs_base_kernel, and you rip it out? I'm curious as to what
> they're going to say...

I didn't find it necessary; I was mostly focused on merging the PVH and 
HVM codepaths without causing any regressions.  It's not obvious to me 
what's special about gs_base_kernel, and I haven't yet gone back to try 
to find out why Mukesh did it that way.

  -George