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

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 22/10/15 15:20, Jan Beulich wrote:
>>>> On 20.10.15 at 10:21, <shuai.ruan@linux.intel.com> 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.

~Andrew