linux-kernel - Re: [PATCH] KVM: arm64: Check cpu_has_spe() before initializing PMSCR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251008124040.GC77665@e132581.arm.com>
Date: Wed, 8 Oct 2025 13:40:40 +0100
From: Leo Yan <leo.yan@....com>
To: Marc Zyngier <maz@...nel.org>
Cc: Mukesh Ojha <mukesh.ojha@....qualcomm.com>,
	Oliver Upton <oliver.upton@...ux.dev>, joey.gouly@....com,
	suzuki.poulose@....com, yuzenghui@...wei.com,
	catalin.marinas@....com, will@...nel.org, alexandru.elisei@....com,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: arm64: Check cpu_has_spe() before initializing
 PMSCR_EL1 in VHE

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