linux-kernel - [PATCH 0/3] avoid unnecessary memslot rmap walks

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Message-Id: <1591128450-11977-1-git-send-email-anthony.yznaga@oracle.com>
Date:   Tue,  2 Jun 2020 13:07:27 -0700
From:   Anthony Yznaga <anthony.yznaga@...cle.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     pbonzini@...hat.com, sean.j.christopherson@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        steven.sistare@...cle.com, anthony.yznaga@...cle.com
Subject: [PATCH 0/3] avoid unnecessary memslot rmap walks

While investigating optimizing qemu start time for large memory guests
I found that kvm_mmu_slot_apply_flags() is walking rmaps to update
existing sptes when creating or moving a slot but that there won't be
any existing sptes to update and any sptes inserted once the new memslot
is visible won't need updating.  I can't find any reason for this not to
be the case, but I've taken a more cautious approach to fixing this by
dividing things into three patches.

Anthony Yznaga (3):
  KVM: x86: remove unnecessary rmap walk of read-only memslots
  KVM: x86: avoid unnecessary rmap walks when creating/moving slots
  KVM: x86: minor code refactor and comments fixup around dirty logging

 arch/x86/kvm/x86.c | 106 +++++++++++++++++++++++++----------------------------
 1 file changed, 49 insertions(+), 57 deletions(-)

-- 
2.13.3