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[34.82.80.254]) by smtp.gmail.com with ESMTPSA id 144sm18889276pgg.4.2021.07.12.11.11.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jul 2021 11:11:10 -0700 (PDT) Date: Mon, 12 Jul 2021 18:11:06 +0000 From: David Matlack To: Ben Gardon Cc: kvm , Joerg Roedel , Jim Mattson , Wanpeng Li , Vitaly Kuznetsov , Sean Christopherson , Paolo Bonzini , Junaid Shahid , Andrew Jones , Matthew Wilcox , Yu Zhao , David Hildenbrand , Andrew Morton Subject: Re: [PATCH v2 3/6] KVM: x86/mmu: Make walk_shadow_page_lockless_{begin,end} interoperate with the TDP MMU Message-ID: References: <20210630214802.1902448-1-dmatlack@google.com> <20210630214802.1902448-4-dmatlack@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Jul 12, 2021 at 10:02:31AM -0700, Ben Gardon wrote: > On Wed, Jun 30, 2021 at 2:48 PM David Matlack wrote: > > > > Acquire the RCU read lock in walk_shadow_page_lockless_begin and release > > it in walk_shadow_page_lockless_end when the TDP MMU is enabled. This > > should not introduce any functional changes but is used in the following > > commit to make fast_page_fault interoperate with the TDP MMU. > > > > Signed-off-by: David Matlack > > Reviewed-by: Ben Gardon > > This as I understand this, we're just lifting the rcu_lock/unlock out > of kvm_tdp_mmu_get_walk, and then putting all the TDP MMU specific > stuff down a level under walk_shadow_page_lockless_begin/end and > get_walk. > > Instead of moving kvm_tdp_mmu_get_walk_lockless into get_walk, it > could also be open-coded as: > > walk_shadow_page_lockless_begin > if (is_tdp_mmu(vcpu->arch.mmu)) > leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root); > else > leaf = get_walk(vcpu, addr, sptes, &root); > walk_shadow_page_lockless_end > > in get_mmio_spte, since get_walk isn't used anywhere else. Then > walk_shadow_page_lockless_begin/end could also be moved up out of > get_walk instead of having to add a goto to that function. > I don't have a strong preference either way, but the above feels like > a slightly simpler refactor. I don't have a strong preference either way as well. I'd be happy to switch to your suggestion in v3.