Re: [PATCH 6/6] s390: scrub registers on kernel entry and KVM exit

Christian Borntraeger
2018-01-19T07:57:51Z

On 01/19/2018 07:29 AM, QingFeng Hao wrote:
>
>
> 在 2018/1/17 17:48, Martin Schwidefsky 写道:
>> Clear all user space registers on entry to the kernel and all KVM guest
>> registers on KVM guest exit if the register does not contain either a
>> parameter or a result value.
> I am not sure if I understand this but it will be safer?

It ist similar to commit 0cb5b30698fd ("kvm: vmx: Scrub hardware GPRs at VM-exit").
The idea is to minimize potential payload channels.

> And can we abstract the operations to be a macro like CLEAR_REG_7?

No, please.
xgr %r7,%r7
is absolutely clear what it does, a MACRO often is not.