linux-kernel - Re: [PATCH 00/28] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing

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Date:   Thu, 2 Dec 2021 16:16:34 -0800
From:   David Matlack <dmatlack@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Hou Wenlong <houwenlong93@...ux.alibaba.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH 00/28] KVM: x86/mmu: Overhaul TDP MMU zapping and flushing

On Wed, Dec 1, 2021 at 6:03 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Wed, Dec 01, 2021, David Matlack wrote:
> > On Fri, Nov 19, 2021 at 8:51 PM Sean Christopherson <seanjc@...gle.com> wrote:
> > >
> > > Overhaul TDP MMU's handling of zapping and TLB flushing to reduce the
> > > number of TLB flushes, and to clean up the zapping code.  The final patch
> > > realizes the biggest change, which is to use RCU to defer any TLB flush
> > > due to zapping a SP to the caller.  The largest cleanup is to separate the
> > > flows for zapping roots (zap _everything_), zapping leaf SPTEs (zap guest
> > > mappings for whatever reason), and zapping a specific SP (NX recovery).
> > > They're currently smushed into a single zap_gfn_range(), which was a good
> > > idea at the time, but became a mess when trying to handle the different
> > > rules, e.g. TLB flushes aren't needed when zapping a root because KVM can
> > > safely zap a root if and only if it's unreachable.
> > >
> > > For booting an 8 vCPU, remote_tlb_flush (requests) goes from roughly
> > > 180 (600) to 130 (215).
> > >
> > > Please don't apply patches 02 and 03, they've been posted elsehwere and by
> > > other people.  I included them here because some of the patches have
> > > pseudo-dependencies on their changes.  Patch 01 is also posted separately.
> > > I had a brain fart and sent it out realizing that doing so would lead to
> > > oddities.
> >
> > What's the base commit for this series?
>
> Pretty sure it's based on a stale kvm/queue, commit 81d7c6659da0 ("KVM: VMX: Remove
> vCPU from PI wakeup list before updating PID.NV").  Time to add useAutoBase=true...

That applied cleanly. Thanks!