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

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Message-Id: <34660999-606f-0cab-6630-4116ad833c77@linux.vnet.ibm.com>
Date:   Fri, 19 Jan 2018 16:27:08 +0800
From:   QingFeng Hao <haoqf@...ux.vnet.ibm.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Heiko Carstens <heiko.carstens@...ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jon Masters <jcm@...hat.com>,
        Marcus Meissner <meissner@...e.de>,
        Jiri Kosina <jkosina@...e.cz>
Subject: Re: [PATCH 6/6] s390: scrub registers on kernel entry and KVM exit



在 2018/1/19 15:57, Christian Borntraeger 写道:
>
> 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.
Got it! thanks for your explanation!
>
>> 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.
nod, this makes sense!

-- 
Regards
QingFeng Hao