Re: [Xen-devel] [PATCH] [v2] xen: Add FS and GS base to HVM VCPU context

[Aravindh Puthiyaparambil <aravindh@xxxxxxxxxxxx>]

On Tue, Apr 24, 2012 at 12:52 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 24.04.12 at 01:16, Aravindh Puthiyaparambil <aravindh@xxxxxxxxxxxx> 
>>>> wrote:
>> Add FS and GS base to the HVM VCPU context returned by xc_vcpu_getcontext()
>>
>> Signed-off-by: Aravindh Puthiyaparambil <aravindh@xxxxxxxxxxxx>
>>
>> diff -r 6ef297a3761f -r f7a1633867bf xen/arch/x86/domctl.c
>> --- a/xen/arch/x86/domctl.c   Mon Apr 23 15:16:34 2012 -0700
>> +++ b/xen/arch/x86/domctl.c   Mon Apr 23 16:12:50 2012 -0700
>> @@ -1590,8 +1590,17 @@ void arch_get_info_guest(struct vcpu *v,
>>          c.nat->user_regs.es = sreg.sel;
>>          hvm_get_segment_register(v, x86_seg_fs, &sreg);
>>          c.nat->user_regs.fs = sreg.sel;
>> +#ifdef __x86_64__
>> +        c.nat->fs_base = sreg.base;
>> +#endif
>>          hvm_get_segment_register(v, x86_seg_gs, &sreg);
>>          c.nat->user_regs.gs = sreg.sel;
>> +#ifdef __x86_64__
>> +        if ( ring_0(&c.nat->user_regs) )
>> +            c.nat->gs_base_kernel = sreg.base;
>> +        else
>> +            c.nat->gs_base_user = sreg.base;
>> +#endif
>
> Which still leaves one of gs_base_* unfilled in all cases. You'll need
> to get ahold of vmcb->kerngsbase (AMD/SVM) or
> v->arch.hvm_vmx.shadow_gs (Intel/VMX). You could either
> introduce a new wrapper, or expose {svm,vmx}_save_cpu_state()
> as a new function table entry, or pay the price of calling
> ->save_cpu_ctxt(). But you will need to pay extra attention to
> the case of the subject vCPU being current.

OK, I will try introducing a new wrapper that will return
vmcb->kerngsbase /  v->arch.hvm_vmx.shadow_gs.

Thanks,
Aravindh

>>      }
>>      else
>>      {
>>
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>
>
>

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