From: Sean Christopherson <seanjc@google.com>
To: Oliver Upton <oupton@google.com>
Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel@lists.infradead.org,
Peter Shier <pshier@google.com>,
Ricardo Koller <ricarkol@google.com>,
Reiji Watanabe <reijiw@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Ben Gardon <bgardon@google.com>,
David Matlack <dmatlack@google.com>
Subject: Re: [RFC PATCH 06/17] KVM: arm64: Implement break-before-make sequence for parallel walks
Date: Mon, 25 Apr 2022 18:16:52 +0000 [thread overview]
Message-ID: <YmbllLTbP0TGDemE@google.com> (raw)
In-Reply-To: <CAOQ_QshYttK+e9PQdp+vZo2w7NN8oGVAQm8LC+DBP5gs+5fLwA@mail.gmail.com>
On Mon, Apr 25, 2022, Oliver Upton wrote:
> On Mon, Apr 25, 2022 at 8:13 AM Sean Christopherson <seanjc@google.com> wrote:
> >
> > On Fri, Apr 15, 2022, Oliver Upton wrote:
> > > The ARM architecture requires that software use the 'break-before-make'
> > > sequence whenever memory is being remapped.
> >
> > What does "remapped" mean here? Changing the pfn? Promoting/demoting to/from a
> > huge page?
>
> Both, but in the case of this series it is mostly concerned with
> promotion/demotion. I'll make this language a bit more precise next
> time around.
Please be very precise :-) It matters because it should be impossible for KVM to
actually change a PFN in a valid PTE. Callers of mmu_notifier_change_pte() are
required to bookend it with mmu_notifier_invalidate_range_start/end(), i.e. KVM
should have zapped all PTEs and should not establish new PTEs. I'd actually like
to drop mmu_notifier_change_pte() altogether, because for all intents and purposes,
it's dead code. But convincing "everyone" that dropping it instead of trying to
salvage it for KSM is too much work :-)
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-04-25 18:18 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YmbllLTbP0TGDemE@google.com \
--to=seanjc@google.com \
--cc=alexandru.elisei@arm.com \
--cc=bgardon@google.com \
--cc=dmatlack@google.com \
--cc=james.morse@arm.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=maz@kernel.org \
--cc=oupton@google.com \
--cc=pbonzini@redhat.com \
--cc=pshier@google.com \
--cc=reijiw@google.com \
--cc=ricarkol@google.com \
--cc=suzuki.poulose@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).