linux-kernel - Re: [PATCH] KVM: x86/mmu: Add "never" option to allow sticky disabling of nx_huge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <abf509a2-ebfd-7b5f-4f7a-fdd4ef60c1de@amazon.com>
Date:   Wed, 14 Jun 2023 09:20:24 -0400
From:   Luiz Capitulino <luizcap@...zon.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
CC:     <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Li RongQing <lirongqing@...du.com>,
        Yong He <zhuangel570@...il.com>,
        Robert Hoo <robert.hoo.linux@...il.com>,
        Kai Huang <kai.huang@...el.com>
Subject: Re: [PATCH] KVM: x86/mmu: Add "never" option to allow sticky
 disabling of nx_huge_pages



On 2023-06-13 19:21, Sean Christopherson wrote:

> 
> 
> 
> On Thu, 01 Jun 2023 17:58:59 -0700, Sean Christopherson wrote:
>> Add a "never" option to the nx_huge_pages module param to allow userspace
>> to do a one-way hard disabling of the mitigation, and don't create the
>> per-VM recovery threads when the mitigation is hard disabled.  Letting
>> userspace pinky swear that userspace doesn't want to enable NX mitigation
>> (without reloading KVM) allows certain use cases to avoid the latency
>> problems associated with spawning a kthread for each VM.
>>
>> [...]
> 
> Applied to kvm-x86 mmu.  I kept the default as "auto" for now, as that can go on
> top and I don't want to introduce that change this late in the cycle.  If no one
> beats me to the punch (hint, hint ;-) ), I'll post a patch to make "never" the
> default for unaffected hosts so that we can discuss/consider that change for 6.6.

Thanks Sean, I agree with the plan. I could give a try on the patch if you'd like.

- Luiz

> 
> Thanks for the reviews!
> 
> [1/1] KVM: x86/mmu: Add "never" option to allow sticky disabling of nx_huge_pages
>        https://github.com/kvm-x86/linux/commit/0b210faf3373
> 
> --
> https://github.com/kvm-x86/linux/tree/next
> https://github.com/kvm-x86/linux/tree/fixes