From: Paolo Bonzini <pbonzini@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH rebase/RFC 0/4] x86/kvm/nVMX: optimize MMU switch between L1 and L2
Date: Tue, 31 Jul 2018 18:52:28 +0200 [thread overview]
Message-ID: <4eb9e84b-c159-3e26-7a91-df2cecd72a9b@redhat.com> (raw)
In-Reply-To: <87bmano0qp.fsf@vitty.brq.redhat.com>
On 31/07/2018 17:58, Vitaly Kuznetsov wrote:
> Thank you for the rebase,
>
> it seems that with multi-root caching this series should just ignore CR3
> changes for both root_mmu and guest_mmu: we now have two separate
> 'prev_roots' caches and these work well. However, we still can optimize
> MMU re-initialization on L1->L2 and L2->L1 switches out using e.g. my
> 'scache' idea (which can be orthogonal to page_role check on CR3).
Indeed, though if possible the scache should be based on the role to
avoid duplicating code and data structures.
(Also I didn't quite have time to figure out _why_ without
root_mmu/guest_mmu there is still contention, it's probably something
trivial).
Paolo
> In my Hyper-V-on-KVM environment I'm seeing an additional 1000 CPU
> cycles win for a nested vmexit.
>
> I'll pull things together and re-send the whole series.
prev parent reply other threads:[~2018-07-31 16:52 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-27 16:56 [PATCH rebase/RFC 0/4] x86/kvm/nVMX: optimize MMU switch between L1 and L2 Paolo Bonzini
2018-07-27 16:56 ` [PATCH 1/4] x86/kvm/mmu: make vcpu->mmu a pointer to the current MMU Paolo Bonzini
2018-07-27 16:56 ` [PATCH 2/4] x86/kvm/mmu.c: set get_pdptr hook in kvm_init_shadow_ept_mmu() Paolo Bonzini
2018-07-27 16:56 ` [PATCH 3/4] x86/kvm/mmu.c: add kvm_mmu parameter to kvm_mmu_free_roots() Paolo Bonzini
2018-07-27 16:56 ` [PATCH 4/4] x86/kvm/mmu: introduce guest_mmu Paolo Bonzini
2018-07-31 15:58 ` [PATCH rebase/RFC 0/4] x86/kvm/nVMX: optimize MMU switch between L1 and L2 Vitaly Kuznetsov
2018-07-31 16:52 ` Paolo Bonzini [this message]
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