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

["Roger Pau Monné" <roger.pau@citrix.com>]

On 15/11/13 17:32, 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.

Without this patch you can set ctrlreg[4] (and ctrlreg[0]), but it's
going to be completely ignored, which is confusing IMHO.

> Apart from that ctrlreg[] is an 8-element array... And I don't
> see debugreg[] being verified at all.

Ack.

> 
>>               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...
> 
>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> @@ -1492,10 +1492,6 @@ static void vmx_set_info_guest(struct vcpu *v, uint64_t gs_base_kernel)
>>          __vmwrite(GUEST_INTERRUPTIBILITY_INFO, intr_shadow);
>>      }
>>  
>> -    /* PVH 32bitfixme */
>> -    if ( is_pvh_vcpu(v) )
>> -        __vmwrite(GUEST_GS_BASE, gs_base_kernel);
> 
> And if you rip it out, then you should remove the now unused
> function parameter here again.

Yes, will wait for other comments and resend.