Re: [Xen-devel] [V7 3/4] x86/xsaves: enable xsaves/xrstors for hvm guest

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.10.15 at 16:26, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 22/10/15 15:20, Jan Beulich wrote:
>>>>> On 20.10.15 at 10:21, <shuai.ruan@xxxxxxxxxxxxxxx> wrote:
>>> @@ -4784,6 +4804,13 @@ int hvm_msr_write_intercept(unsigned int msr, 
>>> uint64_t 
> msr_content,
>>>             return X86EMUL_EXCEPTION;
>>>          break;
>>>  
>>> +    case MSR_IA32_XSS:
>>> +        /* No XSS features currently supported for guests. */
>>> +        if ( !cpu_has_xsaves || msr_content != 0 )
>>> +            goto gp_fault;
>>> +        v->arch.hvm_vcpu.msr_xss = msr_content;
>>> +        break;
>> Considering you add this write (and the msr_xss field in the first place)
>> despite it always being zero, I'd really like you to also add code
>> supporting save/restore of this new MSR. Or did I overlook something?
> 
> I suppose that does mean that we don't strictly need
> interception/management of MSR_IA32_XSS yet, but it is ground work for
> the future work to enable Processor Trace for HVM guests.

Right, that's how I understand it. I simply think that if such ground
work is done, it shouldn't stop half ways.

Jan


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