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

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Message-ID: <ZIoQDbte/uAiit9N@google.com>
Date:   Wed, 14 Jun 2023 12:07:57 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Luiz Capitulino <luizcap@...zon.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, 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 Wed, Jun 14, 2023, Luiz Capitulino wrote:
> 
> 
> 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.

Yes please, thanks!