From: Sebastian Ott <sebott@redhat.com>
To: oliver.upton@linux.dev
Cc: james.morse@arm.com, kvm@vger.kernel.org, kvmarm@lists.linux.dev,
maz@kernel.org, suzuki.poulose@arm.com, yuzenghui@huawei.com
Subject: Re: [PATCH 3/7] KVM: arm64: Only reset vCPU-scoped feature ID regs once
Date: Mon, 13 May 2024 15:31:04 +0200 [thread overview]
Message-ID: <20240513133104.14444-1-sebott@redhat.com> (raw)
In-Reply-To: <20240502233529.1958459-4-oliver.upton@linux.dev>
> The general expecation with feature ID registers is that they're 'reset'
^
expectation
> exactly once by KVM for the lifetime of a vCPU/VM, such that any
> userspace changes to the CPU features / identity are honored after a
> vCPU gets reset (e.g. PSCI_ON).
>
> KVM handles what it calls VM-scoped feature ID registers correctly, but
> feature ID registers local to a vCPU (CLIDR_EL1, MPIDR_EL1) get wiped
> after every reset. What's especially concerning is that a
> potentially-changing MPIDR_EL1 breaks MPIDR compression for indexing
> mpidr_data, as the mask of useful bits to build the index could change.
>
> This is absolutely no good. Avoid resetting vCPU feature ID registers
> more than once.
Reviewed-by: Sebastian Ott <sebott@redhat.com>
next prev parent reply other threads:[~2024-05-13 13:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-02 23:35 [PATCH 0/7] KVM: arm64: Don't clobber CLIDR and MPIDR across vCPU reset Oliver Upton
2024-05-02 23:35 ` [PATCH 1/7] KVM: arm64: Rename is_id_reg() to imply VM scope Oliver Upton
2024-05-13 13:24 ` Sebastian Ott
2024-05-02 23:35 ` [PATCH 2/7] KVM: arm64: Reset VM feature ID regs from kvm_reset_sys_regs() Oliver Upton
2024-05-13 13:26 ` Sebastian Ott
2024-05-02 23:35 ` [PATCH 3/7] KVM: arm64: Only reset vCPU-scoped feature ID regs once Oliver Upton
2024-05-13 13:31 ` Sebastian Ott [this message]
2024-05-02 23:35 ` [PATCH 4/7] KVM: selftests: Rename helper in set_id_regs to imply VM scope Oliver Upton
2024-05-02 23:35 ` [PATCH 5/7] KVM: selftests: Store expected register value in set_id_regs Oliver Upton
2024-05-02 23:35 ` [PATCH 6/7] KVM: arm64: Test that feature ID regs survive a reset Oliver Upton
2024-05-02 23:35 ` [PATCH 7/7] KVM: selftests: Test vCPU-scoped feature ID registers Oliver Upton
2024-05-09 17:45 ` [PATCH 0/7] KVM: arm64: Don't clobber CLIDR and MPIDR across vCPU reset Marc Zyngier
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=20240513133104.14444-1-sebott@redhat.com \
--to=sebott@redhat.com \
--cc=james.morse@arm.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.linux.dev \
--cc=maz@kernel.org \
--cc=oliver.upton@linux.dev \
--cc=suzuki.poulose@arm.com \
--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 read-only IMAP folder(s) and NNTP newsgroup(s).