From: Quentin Perret <qperret@google.com>
To: Oliver Upton <oupton@google.com>
Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
Marc Zyngier <maz@kernel.org>, Ben Gardon <bgardon@google.com>,
Peter Shier <pshier@google.com>,
David Matlack <dmatlack@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 09/17] KVM: arm64: Tear down unlinked page tables in parallel walk
Date: Fri, 22 Apr 2022 16:00:45 +0000 [thread overview]
Message-ID: <YmLRLf2GQSgA97Kr@google.com> (raw)
In-Reply-To: <YmGJGIrNVmdqYJj8@google.com>
On Thursday 21 Apr 2022 at 16:40:56 (+0000), Oliver Upton wrote:
> The other option would be to not touch the subtree at all until the rcu
> callback, as at that point software will not tweak the tables any more.
> No need for atomics/spinning and can just do a boring traversal.
Right that is sort of what I had in mind. Note that I'm still trying to
make my mind about the overall approach -- I can see how RCU protection
provides a rather elegant solution to this problem, but this makes the
whole thing inaccessible to e.g. pKVM where RCU is a non-starter. A
possible alternative that comes to mind would be to have all walkers
take references on the pages as they walk down, and release them on
their way back, but I'm still not sure how to make this race-safe. I'll
have a think ...
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next prev parent reply other threads:[~2022-04-22 16:05 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-15 21:58 [RFC PATCH 00/17] KVM: arm64: Parallelize stage 2 fault handling Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 01/17] KVM: arm64: Directly read owner id field in stage2_pte_is_counted() Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 02/17] KVM: arm64: Only read the pte once per visit Oliver Upton
2022-04-21 16:12 ` Ben Gardon
2022-04-15 21:58 ` [RFC PATCH 03/17] KVM: arm64: Return the next table from map callbacks Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 04/17] KVM: arm64: Protect page table traversal with RCU Oliver Upton
2022-04-19 2:55 ` Ricardo Koller
2022-04-19 3:01 ` Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 05/17] KVM: arm64: Take an argument to indicate parallel walk Oliver Upton
2022-04-16 11:30 ` Marc Zyngier
2022-04-16 16:03 ` Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 06/17] KVM: arm64: Implement break-before-make sequence for parallel walks Oliver Upton
2022-04-20 16:55 ` Quentin Perret
2022-04-20 17:06 ` Oliver Upton
2022-04-21 16:57 ` Ben Gardon
2022-04-21 18:52 ` Oliver Upton
2022-04-26 21:32 ` Ben Gardon
2022-04-25 15:13 ` Sean Christopherson
2022-04-25 16:53 ` Oliver Upton
2022-04-25 18:16 ` Sean Christopherson
2022-04-15 21:58 ` [RFC PATCH 07/17] KVM: arm64: Enlighten perm relax path about " Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 08/17] KVM: arm64: Spin off helper for initializing table pte Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 09/17] KVM: arm64: Tear down unlinked page tables in parallel walk Oliver Upton
2022-04-21 13:21 ` Quentin Perret
2022-04-21 16:40 ` Oliver Upton
2022-04-22 16:00 ` Quentin Perret [this message]
2022-04-22 20:41 ` Oliver Upton
2022-05-03 14:17 ` Quentin Perret
2022-05-04 6:03 ` Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 10/17] KVM: arm64: Assume a table pte is already owned in post-order traversal Oliver Upton
2022-04-21 16:11 ` Ben Gardon
2022-04-21 17:16 ` Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 11/17] KVM: arm64: Move MMU cache init/destroy into helpers Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 12/17] KVM: arm64: Stuff mmu page cache in sub struct Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 13/17] KVM: arm64: Setup cache for stage2 page headers Oliver Upton
2022-04-15 21:58 ` [RFC PATCH 14/17] KVM: arm64: Punt last page reference to rcu callback for parallel walk Oliver Upton
2022-04-19 2:59 ` Ricardo Koller
2022-04-19 3:09 ` Ricardo Koller
2022-04-20 0:53 ` Oliver Upton
2022-09-08 0:52 ` David Matlack
2022-04-21 16:28 ` Ben Gardon
2022-04-15 21:58 ` [RFC PATCH 15/17] KVM: arm64: Allow parallel calls to kvm_pgtable_stage2_map() Oliver Upton
2022-04-15 21:59 ` [RFC PATCH 16/17] KVM: arm64: Enable parallel stage 2 MMU faults Oliver Upton
2022-04-21 16:35 ` Ben Gardon
2022-04-21 16:46 ` Oliver Upton
2022-04-21 17:03 ` Ben Gardon
2022-04-15 21:59 ` [RFC PATCH 17/17] TESTONLY: KVM: arm64: Add super lazy accounting of stage 2 table pages Oliver Upton
2022-04-15 23:35 ` [RFC PATCH 00/17] KVM: arm64: Parallelize stage 2 fault handling David Matlack
2022-04-16 0:04 ` Oliver Upton
2022-04-21 16:43 ` David Matlack
2022-04-16 6:23 ` Oliver Upton
2022-04-19 17:57 ` Ben Gardon
2022-04-19 18:36 ` Oliver Upton
2022-04-21 16:30 ` Ben Gardon
2022-04-21 16:37 ` Paolo Bonzini
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