arm64: errata: Mitigate TLBI errata on various Arm CPUs

[pelwell]

[ Early port of patch sent to linux-arm-kernel, minus documentation ]

A number of CPUs developed by Arm suffer from errata whereby a broadcast TLBI;DSB sequence may complete before the global observation of writes which are translated by an affected TLB entry.

These errata ONLY affect the completion of memory accesses which have been translated by an invalidated TLB entry, and these errata DO NOT affect the actual invalidation of TLB entries. TLB entries are removed correctly.

This issue has been assigned CVE ID CVE-2025-10263.

To mitigate this issue, Arm recommends that software follows any affected TLBI;DSB sequence with an additional TLBI;DSB, which will ensure that all memory write effects affected by the first TLBI have been globally observed. The additional TLBI can use any operation that is broadcast to affected CPUs, and the additional DSB can use any option that is sufficient to complete the additional TLBI.

The ARM64_WORKAROUND_REPEAT_TLBI workaround is sufficient to mitigate the issue. Enable this workaround for affected CPUs, and update the silicon errata documentation accordingly.

Note that due to the manner in which Arm develops IP and tracks errata, some CPUs share a common erratum number.

Cc: Catalin Marinas catalin.marinas@arm.com
Cc: Will Deacon will@kernel.org

[pelwell]

@Kletternaut This is a new performance regression that is probably coming down the pipe. I'm curious about how running this kernel (sudo rpi-update pulls/7429, after reading the caveats) affects your use cases.