From: Oliver Upton <oliver.upton@linux.dev>
To: Jing Zhang <jingzhangos@google.com>
Cc: KVM <kvm@vger.kernel.org>, KVMARM <kvmarm@lists.linux.dev>,
ARMLinux <linux-arm-kernel@lists.infradead.org>,
Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Fuad Tabba <tabba@google.com>, Reiji Watanabe <reijiw@google.com>,
Raghavendra Rao Ananta <rananta@google.com>,
Suraj Jitindar Singh <surajjs@amazon.com>,
Cornelia Huck <cohuck@redhat.com>
Subject: Re: [PATCH v6 2/6] KVM: arm64: Reject attempts to set invalid debug arch version
Date: Fri, 21 Jul 2023 21:18:17 +0000 [thread overview]
Message-ID: <ZLr2GXAgj5Y/fdJw@linux.dev> (raw)
In-Reply-To: <20230718164522.3498236-3-jingzhangos@google.com>
On Tue, Jul 18, 2023 at 04:45:18PM +0000, Jing Zhang wrote:
> From: Oliver Upton <oliver.upton@linux.dev>
>
> The debug architecture is mandatory in ARMv8, so KVM should not allow
> userspace to configure a vCPU with less than that. Of course, this isn't
> handled elegantly by the generic ID register plumbing, as the respective
> ID register fields have a nonzero starting value.
>
> Add an explicit check for debug versions less than v8 of the
> architecture.
>
> Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> Signed-off-by: Jing Zhang <jingzhangos@google.com>
This patch needs to be broken up. You're doing a couple things:
1) Forcing the behavior of the DebugVer field to be FTR_LOWER_SAFE, and
adding the necessary check for a valid version
2) Changing KVM's value for the field to expose up to Debugv8p8 to the
guest.
The latter isn't described in the changelog at all, and worse yet the
ordering of the series is not bisectable. Changing the default value of
the field w/o allowing writes breaks migration.
So, please split this patch in two and consider stacking like so:
- Change #1 above (field sanitization)
- "KVM: arm64: Enable writable for ID_AA64DFR0_EL1 and ID_DFR0_EL1"
- Change #2 above (advertise up to v8p8)
--
Thanks,
Oliver
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next prev parent reply other threads:[~2023-07-21 21:18 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-18 16:45 [PATCH v6 0/6] Enable writable for idregs DFR0,PFR0, MMFR{0,1,2, 3} Jing Zhang
2023-07-18 16:45 ` [PATCH v6 1/6] KVM: arm64: Use guest ID register values for the sake of emulation Jing Zhang
2023-07-18 16:45 ` [PATCH v6 2/6] KVM: arm64: Reject attempts to set invalid debug arch version Jing Zhang
2023-07-21 21:18 ` Oliver Upton [this message]
2023-07-21 22:26 ` Jing Zhang
2023-07-18 16:45 ` [PATCH v6 3/6] KVM: arm64: Enable writable for ID_AA64DFR0_EL1 and ID_DFR0_EL1 Jing Zhang
2023-07-20 8:52 ` Cornelia Huck
2023-07-20 16:39 ` Jing Zhang
2023-07-21 8:38 ` Cornelia Huck
2023-07-21 9:31 ` Marc Zyngier
2023-07-21 9:48 ` Cornelia Huck
2023-07-29 10:36 ` Marc Zyngier
2023-07-31 20:51 ` Jing Zhang
2023-07-21 18:22 ` Jing Zhang
2023-07-21 21:10 ` Oliver Upton
[not found] ` <87edkxg0jr.fsf@redhat.com>
[not found] ` <ZMFWsvWzfkkz2VNB@thinky-boi>
2023-07-27 9:34 ` Cornelia Huck
2023-07-18 16:45 ` [PATCH v6 4/6] KVM: arm64: Enable writable for ID_AA64PFR0_EL1 Jing Zhang
2023-07-18 16:45 ` [PATCH v6 5/6] KVM: arm64: Enable writable for ID_AA64MMFR{0, 1, 2, 3}_EL1 Jing Zhang
2023-07-18 16:45 ` [PATCH v6 6/6] KVM: arm64: selftests: Test for setting ID register from usersapce Jing Zhang
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