From: Marc Zyngier <maz@kernel.org>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: James Morse <james.morse@arm.com>,
linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
Quentin Perret <qperret@google.com>,
Will Deacon <will@kernel.org>, Reiji Watanabe <reijiw@google.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH 3/5] KVM: arm64: Only return attributes from stage2_update_leaf_attrs()
Date: Wed, 11 Jan 2023 08:52:25 +0000 [thread overview]
Message-ID: <87ilhde9me.wl-maz@kernel.org> (raw)
In-Reply-To: <20230111000300.2034799-4-oliver.upton@linux.dev>
[+ Suzuki and Zenghui who are missing from the Cc list]
On Wed, 11 Jan 2023 00:02:58 +0000,
Oliver Upton <oliver.upton@linux.dev> wrote:
>
> Returning a single PTE from stage2_update_leaf_attrs() doesn't make a
> great deal of sense given that the function could be used to apply a
> change to a range of PTEs. Instead, return a bitwise OR of attributes
> from all the visited PTEs.
I find this amalgamation of attributes quite confusing, and I have a
hard time attaching semantics to the resulting collection of bits.
It also means that you cannot reason about a particular attribute
being 0 if any of the neighbour PTEs has this bit set.
>
> As the walker is no longer returning the full PTE, drop the check for a
> valid PTE in kvm_age_gfn().
But then what does it mean to check for a potentially invalid PTE?
The helpers explicitly say:
/*
* The following only work if pte_present(). Undefined behaviour otherwise.
*/
#define pte_present(pte) (!!(pte_val(pte) & (PTE_VALID | PTE_PROT_NONE)))
#define pte_young(pte) (!!(pte_val(pte) & PTE_AF))
and you seem to be violating this requirement.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
_______________________________________________
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:[~2023-01-11 8:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-11 0:02 [PATCH 0/5] KVM: arm64: Handle unaligned memslots in kvm_(test_)_age_gfn() Oliver Upton
2023-01-11 0:02 ` [PATCH 1/5] KVM: arm64: Hoist S2 PTE definitions into kvm_pgtable.h Oliver Upton
2023-01-11 0:02 ` [PATCH 2/5] KVM: arm64: Add a mask for all leaf PTE attributes Oliver Upton
2023-01-11 0:02 ` [PATCH 3/5] KVM: arm64: Only return attributes from stage2_update_leaf_attrs() Oliver Upton
2023-01-11 8:52 ` Marc Zyngier [this message]
2023-01-11 17:21 ` Oliver Upton
2023-02-02 22:08 ` Oliver Upton
2023-02-07 14:56 ` Marc Zyngier
2023-01-11 0:02 ` [PATCH 4/5] KVM: arm64: Correctly handle page aging notifiers for unaligned memlsot Oliver Upton
2023-01-12 15:44 ` Marc Zyngier
2023-01-11 0:03 ` [PATCH 5/5] KVM: arm64: Consistently use KVM's types/helpers in kvm_age_gfn() Oliver Upton
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=87ilhde9me.wl-maz@kernel.org \
--to=maz@kernel.org \
--cc=james.morse@arm.com \
--cc=kvmarm@lists.linux.dev \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=oliver.upton@linux.dev \
--cc=qperret@google.com \
--cc=reijiw@google.com \
--cc=suzuki.poulose@arm.com \
--cc=will@kernel.org \
--cc=yuzenghui@huawei.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).