From: Sean Christopherson <seanjc@google.com>
To: Luiz Capitulino <luizcap@amazon.com>
Cc: stable@vger.kernel.org, christophe.jaillet@wanadoo.fr,
lcapitulino@gmail.com, Li RongQing <lirongqing@baidu.com>,
Yong He <zhuangel570@gmail.com>,
Robert Hoo <robert.hoo.linux@gmail.com>,
Kai Huang <kai.huang@intel.com>
Subject: Re: [PATH 6.1.y 2/2] KVM: x86/mmu: Add "never" option to allow sticky disabling of nx_huge_pages
Date: Tue, 5 Sep 2023 17:02:43 -0700 [thread overview]
Message-ID: <ZPfBoxgiQvbWias3@google.com> (raw)
In-Reply-To: <896dfcaf899a30ddf187ba3eccc1c8d47365b973.1693593288.git.luizcap@amazon.com>
On Fri, Sep 01, 2023, Luiz Capitulino wrote:
> From: Sean Christopherson <seanjc@google.com>
>
> Commit 0b210faf337314e4bc88e796218bc70c72a51209 upstream.
>
> [ Resolved a small conflict in arch/x86/kvm/mmu/mmu.c::kvm_mmu_post_init_vm()
> which is due kvm_nx_lpage_recovery_worker() being renamed in upstream
> commit 55c510e26ab6181c132327a8b90c864e6193ce27 ]
>
> 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.
>
> E.g. in FaaS use cases, the guest kernel is trusted and the host may
> create 100+ VMs per logical CPU, which can result in 100ms+ latencies when
> a burst of VMs is created.
>
> Reported-by: Li RongQing <lirongqing@baidu.com>
> Closes: https://lore.kernel.org/all/1679555884-32544-1-git-send-email-lirongqing@baidu.com
> Cc: Yong He <zhuangel570@gmail.com>
> Cc: Robert Hoo <robert.hoo.linux@gmail.com>
> Cc: Kai Huang <kai.huang@intel.com>
> Reviewed-by: Robert Hoo <robert.hoo.linux@gmail.com>
> Acked-by: Kai Huang <kai.huang@intel.com>
> Tested-by: Luiz Capitulino <luizcap@amazon.com>
> Reviewed-by: Li RongQing <lirongqing@baidu.com>
> Link: https://lore.kernel.org/r/20230602005859.784190-1-seanjc@google.com
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Luiz Capitulino <luizcap@amazon.com>
> ---
Acked-by: Sean Christopherson <seanjc@google.com>
next prev parent reply other threads:[~2023-09-06 0:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-01 18:34 [PATH 6.1.y 0/2] Backport KVM's nx_huge_pages=never module parameter Luiz Capitulino
2023-09-01 18:34 ` [PATH 6.1.y 1/2] KVM: x86/mmu: Use kstrtobool() instead of strtobool() Luiz Capitulino
2023-09-06 0:01 ` Sean Christopherson
2023-09-01 18:34 ` [PATH 6.1.y 2/2] KVM: x86/mmu: Add "never" option to allow sticky disabling of nx_huge_pages Luiz Capitulino
2023-09-06 0:02 ` Sean Christopherson [this message]
2023-09-02 7:27 ` [PATH 6.1.y 0/2] Backport KVM's nx_huge_pages=never module parameter Greg KH
2023-09-03 17:28 ` Luiz Capitulino
2023-09-07 11:25 ` Greg KH
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