Re: [PATCH v3 7/7] x86/kvm: use Enlightened VMCS when running on Hyper-V

[Vitaly Kuznetsov]

Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx> writes:

> 2018-03-15 18:02+0100, Radim KrÄmÃÅ:
>> We actually already have mov in the assembly:
>> 
>>   "cmp %%" _ASM_SP ", %c[host_rsp](%0) \n\t"
>
> Oh hell, I didn't pay attention to this line before.
>

This is still going to work if we conditionally replace it with pointer
to evmcs as you suggested before but ...


>>   "je 1f \n\t"
>>   "mov %%" _ASM_SP ", %c[host_rsp](%0) \n\t" // here
>>   __ex(ASM_VMX_VMWRITE_RSP_RDX) "\n\t"
>
> I bet this path is executed only once in VM's lifetime and what we're
> doing is wasting more resources than we're ever going to save ...
>

yes, we're not gonna save anything...

-- 
  Vitaly