Re: [PATCH v2] KVM: x86: use wrpkru directly in kvm_load_{guest|host}_xsave_state

[Jon Kohler]

> On May 11, 2021, at 1:08 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> 
> On 11/05/21 18:45, Dave Hansen wrote:
>> On 5/11/21 8:59 AM, Jon Kohler wrote:
>>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
>>> index b1099f2d9800..20f1fb8be7ef 100644
>>> --- a/arch/x86/include/asm/pgtable.h
>>> +++ b/arch/x86/include/asm/pgtable.h
>>> @@ -151,7 +151,7 @@ static inline void write_pkru(u32 pkru)
>>>  	fpregs_lock();
>>>  	if (pk)
>>>  		pk->pkru = pkru;
>>> -	__write_pkru(pkru);
>>> +	wrpkru(pkru);
>>>  	fpregs_unlock();
>>>  }
>> This removes the:
>> 	if (pkru == rdpkru())
>> 		return;
>> optimization from a couple of write_pkru() users:
>> arch_set_user_pkey_access() and copy_init_pkru_to_fpregs().
>> Was that intentional?  Those aren't the hottest paths in the kernel, but
>> copy_init_pkru_to_fpregs() is used in signal handling and exeve().
> 
> Yeah, you should move it from __write_pkru() to write_pkru() but not remove it completely.
> 
> Paolo

Thanks, Paolo. Just sent out a v3 with that fix up included, so all of
the previous callers should be at par and not notice any differences