From: Marc Zyngier <maz@kernel.org>
To: Quentin Perret <qperret@google.com>
Cc: kernel-team@android.com, qwandor@google.com, will@kernel.org,
catalin.marinas@arm.com, linux-kernel@vger.kernel.org,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 05/14] KVM: arm64: Don't overwrite ignored bits with owner id
Date: Tue, 20 Jul 2021 09:46:51 +0100 [thread overview]
Message-ID: <874kcp9xtw.wl-maz@kernel.org> (raw)
In-Reply-To: <YPWAeTJMWJ+A7W2c@google.com>
On Mon, 19 Jul 2021 14:39:05 +0100,
Quentin Perret <qperret@google.com> wrote:
>
> On Monday 19 Jul 2021 at 13:55:29 (+0100), Marc Zyngier wrote:
> > On Mon, 19 Jul 2021 11:47:26 +0100,
> > Quentin Perret <qperret@google.com> wrote:
> > >
> > > The nVHE protected mode uses invalid mappings in the host stage-2
> > > page-table to track the owner of each page in the system. In order to
> > > allow the usage of ignored bits (a.k.a. software bits) in these
> > > mappings, move the owner encoding away from the top bits.
> >
> > But that's exactly what the current situation is allowing: the use of
> > the SW bits. I am guessing that what you really mean is that you want
> > to *preserve* the SW bits from an existing mapping and use other bits
> > when the mapping is invalid?
>
> Yes, this is really just forward looking, but I think it might be useful
> to allow annotating invalid mappings with both an owner id _and_
> additional flags for e.g. shared pages and such. And using bits [58-55]
> to store those flags just like we do for valid mappings should make
> things easier, but no big deal.
Right, so maybe worth calling that out.
> I see how this is going to conflict with kvm_pgtable_stage2_annotate()
> from your series though, so maybe I should just drop this patch and
> leave the encoding 'issue' to the caller -- the rest of the series
> doesn't depend on this anyway, this was just small cleanup.
I'm not too worried about that for now. We can always rewrite one in
terms of the other, but I wanted to understand exactly this change was
about.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2021-07-20 8:46 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 10:47 [PATCH 00/14] Track shared pages at EL2 in protected mode Quentin Perret
2021-07-19 10:47 ` [PATCH 01/14] KVM: arm64: Provide the host_stage2_try() helper macro Quentin Perret
2021-07-20 13:57 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 02/14] KVM: arm64: Optimize kvm_pgtable_stage2_find_range() Quentin Perret
2021-07-19 10:47 ` [PATCH 03/14] KVM: arm64: Continue stage-2 map when re-creating mappings Quentin Perret
2021-07-19 12:14 ` Marc Zyngier
2021-07-19 13:32 ` Quentin Perret
2021-07-20 8:26 ` Marc Zyngier
2021-07-20 11:56 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 04/14] KVM: arm64: Rename KVM_PTE_LEAF_ATTR_S2_IGNORED Quentin Perret
2021-07-19 10:47 ` [PATCH 05/14] KVM: arm64: Don't overwrite ignored bits with owner id Quentin Perret
2021-07-19 12:55 ` Marc Zyngier
2021-07-19 13:39 ` Quentin Perret
2021-07-20 8:46 ` Marc Zyngier [this message]
2021-07-19 10:47 ` [PATCH 06/14] KVM: arm64: Tolerate re-creating hyp mappings to set ignored bits Quentin Perret
2021-07-20 10:17 ` Fuad Tabba
2021-07-20 10:30 ` Quentin Perret
2021-07-20 10:59 ` Fuad Tabba
2021-07-20 11:14 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 07/14] KVM: arm64: Enable forcing page-level stage-2 mappings Quentin Perret
2021-07-19 14:24 ` Marc Zyngier
2021-07-19 15:36 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 08/14] KVM: arm64: Add support for tagging shared pages in page-table Quentin Perret
2021-07-19 14:43 ` Marc Zyngier
2021-07-19 15:49 ` Quentin Perret
2021-07-20 10:13 ` Marc Zyngier
2021-07-20 11:48 ` Quentin Perret
2021-07-20 13:48 ` Fuad Tabba
2021-07-20 14:06 ` Quentin Perret
2021-07-21 7:34 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 09/14] KVM: arm64: Mark host bss and rodata section as shared Quentin Perret
2021-07-19 15:01 ` Marc Zyngier
2021-07-19 15:56 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 10/14] KVM: arm64: Enable retrieving protections attributes of PTEs Quentin Perret
2021-07-19 10:47 ` [PATCH 11/14] KVM: arm64: Expose kvm_pte_valid() helper Quentin Perret
2021-07-21 8:20 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 12/14] KVM: arm64: Refactor pkvm_pgtable locking Quentin Perret
2021-07-21 8:37 ` Fuad Tabba
2021-07-19 10:47 ` [PATCH 13/14] KVM: arm64: Restrict hyp stage-1 manipulation in protected mode Quentin Perret
2021-07-21 10:45 ` Fuad Tabba
2021-07-21 13:35 ` Quentin Perret
2021-07-19 10:47 ` [PATCH 14/14] KVM: arm64: Prevent late calls to __pkvm_create_private_mapping() Quentin Perret
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