From: Leo Yan <leo.yan@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Mukesh Ojha <mukesh.ojha@oss.qualcomm.com>,
Oliver Upton <oliver.upton@linux.dev>,
joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com,
catalin.marinas@arm.com, will@kernel.org,
alexandru.elisei@arm.com, linux-arm-kernel@lists.infradead.org,
kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: arm64: Check cpu_has_spe() before initializing PMSCR_EL1 in VHE
Date: Wed, 8 Oct 2025 13:40:40 +0100 [thread overview]
Message-ID: <20251008124040.GC77665@e132581.arm.com> (raw)
In-Reply-To: <861pndzn4w.wl-maz@kernel.org>
On Wed, Oct 08, 2025 at 11:46:55AM +0100, Marc Zyngier wrote:
[...]
> > > Lets guard the change with cpu_has_spe() check so that it only affects
> > > the cpu which has SPE feature supported.
> >
> > This could benefit from being spelled out a bit more. In both cases we
> > check for the presence of FEAT_SPE, however I believe the issue you
> > observe is EL3 hasn't delegated ownership of the Profiling Buffer to
> > Non-secure nor does it reinject an UNDEF in response to the sysreg trap.
> >
> > I agree that the change is correct but the rationale needs to be clear.
>
> To me, this smells a lot more like some sort of papering over a
> firmware bug. Why isn't SPE available the first place?
TF-a grants permission to non-secure world [1], only access from secure
world or realm will trap to EL3.
So yes, it would be good to check if any issue in firmware.
Thanks,
Leo
[1] https://git.trustedfirmware.org/plugins/gitiles/TF-A/trusted-firmware-a.git/+/refs/heads/master/lib/extensions/spe/spe.c#52
next prev parent reply other threads:[~2025-10-08 12:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-07 18:23 [PATCH] KVM: arm64: Check cpu_has_spe() before initializing PMSCR_EL1 in VHE Mukesh Ojha
2025-10-07 18:31 ` Oliver Upton
2025-10-08 10:46 ` Marc Zyngier
2025-10-08 12:40 ` Leo Yan [this message]
2025-10-08 16:50 ` Mukesh Ojha
2025-10-08 18:17 ` Leo Yan
2025-10-08 18:26 ` Oliver Upton
2025-10-09 9:11 ` Suzuki K Poulose
2025-10-08 11:53 ` Mukesh Ojha
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