From: Oliver Upton <oliver.upton@linux.dev>
To: Akihiko Odaki <akihiko.odaki@daynix.com>
Cc: Mark Brown <broonie@kernel.org>, Marc Zyngier <maz@kernel.org>,
linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
James Morse <james.morse@arm.com>, Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
asahi@lists.linux.dev, Alyssa Rosenzweig <alyssa@rosenzweig.io>,
Sven Peter <sven@svenpeter.dev>, Hector Martin <marcan@marcan.st>
Subject: Re: [PATCH v4 6/7] KVM: arm64: Mask FEAT_CCIDX
Date: Thu, 5 Jan 2023 20:48:25 +0000 [thread overview]
Message-ID: <Y7c3mQS1zqw0UATF@google.com> (raw)
In-Reply-To: <20221221204016.658874-7-akihiko.odaki@daynix.com>
Hi Akihiko,
On Thu, Dec 22, 2022 at 05:40:15AM +0900, Akihiko Odaki wrote:
> The CCSIDR access handler masks the associativity bits according to the
> bit layout for processors without FEAT_CCIDX. KVM also assumes CCSIDR is
> 32-bit where it will be 64-bit if FEAT_CCIDX is enabled. Mask FEAT_CCIDX
> so that these assumptions hold.
>
> Suggested-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
> ---
> arch/arm64/kvm/sys_regs.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index f4a7c5abcbca..aeabf1f3370b 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1124,6 +1124,12 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r
> ID_DFR0_PERFMON_SHIFT,
> kvm_vcpu_has_pmu(vcpu) ? ID_DFR0_PERFMON_8_4 : 0);
> break;
> + case SYS_ID_AA64MMFR2_EL1:
> + val &= ~ID_AA64MMFR2_EL1_CCIDX_MASK;
> + break;
> + case SYS_ID_MMFR4_EL1:
> + val &= ~ARM64_FEATURE_MASK(ID_MMFR4_CCIDX);
> + break;
Not that it is necessarily worth addressing, but I wanted to point
something out.
This change breaks migration from older kernels on implementations w/
FEAT_CCIDX. There is most likely exactly 0 of those in the wild, but
we need to be careful changing user-visible stuff like this.
--
Thanks,
Oliver
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next prev parent reply other threads:[~2023-01-05 23:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-21 20:40 [PATCH v4 0/7] KVM: arm64: Normalize cache configuration Akihiko Odaki
2022-12-21 20:40 ` [PATCH v4 1/7] arm64: Allow the definition of UNKNOWN system register fields Akihiko Odaki
2022-12-21 20:40 ` [PATCH v4 2/7] arm64/sysreg: Convert CCSIDR_EL1 to automatic generation Akihiko Odaki
2022-12-22 11:45 ` Mark Brown
2022-12-21 20:40 ` [PATCH v4 3/7] arm64/sysreg: Add CCSIDR2_EL1 Akihiko Odaki
2022-12-21 20:40 ` [PATCH v4 4/7] arm64/cache: Move CLIDR macro definitions Akihiko Odaki
2022-12-21 20:40 ` [PATCH v4 5/7] KVM: arm64: Always set HCR_TID2 Akihiko Odaki
2022-12-21 20:40 ` [PATCH v4 6/7] KVM: arm64: Mask FEAT_CCIDX Akihiko Odaki
2023-01-05 20:48 ` Oliver Upton [this message]
2022-12-21 20:40 ` [PATCH v4 7/7] KVM: arm64: Normalize cache configuration Akihiko Odaki
2022-12-25 13:45 ` Marc Zyngier
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