[PATCH v5] arm64: Don't read GMID_EL1 when MTE is disabled

[Will Deacon]

On Thu, 27 Aug 2026 19:59:37 +0100, Fuad Tabba wrote:
> __cpuinfo_store_cpu() gates the GMID_EL1 read on the raw
> ID_AA64PFR1_EL1, so it reads the register even when the kernel has
> disabled MTE (CONFIG_ARM64_MTE=n or arm64.nomte). KVM sets HCR_EL2.TID5
> in that case, and pKVM injects an UNDEF the host cannot handle:
> 
>   Internal error: Oops - Undefined instruction: 0000000002000000 [#1]  SMP
>   pc : __cpuinfo_store_cpu+0xf4/0x264
>   Kernel panic - not syncing: Attempted to kill the idle task!
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/1] arm64: Don't read GMID_EL1 when MTE is disabled
      https://git.kernel.org/arm64/c/5445d6419962

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev