Re: [PATCH AUTOSEL 6.4 07/12] arm64: cpufeature: detect FEAT_HCX

From: Mark Brown
Date: Mon Jul 03 2023 - 07:52:13 EST


On Sun, Jul 02, 2023 at 03:50:52PM -0400, Sasha Levin wrote:
> From: Kristina Martsenko <kristina.martsenko@xxxxxxx>
>
> [ Upstream commit b0c756fe996ac930033882ca56410639e5cad1ec ]
>
> Detect if the system has the new HCRX_EL2 register added in ARMv8.7/9.2,
> so that subsequent patches can check for its presence.
>
> KVM currently relies on the register being present on all CPUs (or
> none), so the kernel will panic if that is not the case. Fortunately no
> such systems currently exist, but this can be revisited if they appear.
> Note that the kernel will not panic if CONFIG_KVM is disabled.

This is a new feature, it's not clear why we'd backport it (especially
since it's a new feature which is a dependency for other features rather
than something that people can use outside of the kernel)?

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