A number of Arm Ltd CPUs suffer from errata whereby an MSR to the SSBS
special-purpose register does not affect subsequent speculative
instructions, permitting speculative store bypassing for a window of
time.
We worked around this for a number of CPUs in commits:
* 7187bb7d0b ("arm64: errata: Add workaround for Arm errata 3194386 and 3312417")
* 75b3c43eab ("arm64: errata: Expand speculative SSBS workaround")
Since then, similar errata have been published for a number of other Arm
Ltd CPUs, for which the same mitigation is sufficient. This is described
in their respective Software Developer Errata Notice (SDEN) documents:
* Cortex-A76 (MP052) SDEN v31.0, erratum 3324349
https://developer.arm.com/documentation/SDEN-885749/3100/
* Cortex-A77 (MP074) SDEN v19.0, erratum 3324348
https://developer.arm.com/documentation/SDEN-1152370/1900/
* Cortex-A78 (MP102) SDEN v21.0, erratum 3324344
https://developer.arm.com/documentation/SDEN-1401784/2100/
* Cortex-A78C (MP138) SDEN v16.0, erratum 3324346
https://developer.arm.com/documentation/SDEN-1707916/1600/
* Cortex-A78C (MP154) SDEN v10.0, erratum 3324347
https://developer.arm.com/documentation/SDEN-2004089/1000/
* Cortex-A725 (MP190) SDEN v5.0, erratum 3456106
https://developer.arm.com/documentation/SDEN-2832921/0500/
* Cortex-X1 (MP077) SDEN v21.0, erratum 3324344
https://developer.arm.com/documentation/SDEN-1401782/2100/
* Cortex-X1C (MP136) SDEN v16.0, erratum 3324346
https://developer.arm.com/documentation/SDEN-1707914/1600/
* Neoverse-N1 (MP050) SDEN v32.0, erratum 3324349
https://developer.arm.com/documentation/SDEN-885747/3200/
* Neoverse-V1 (MP076) SDEN v19.0, erratum 3324341
https://developer.arm.com/documentation/SDEN-1401781/1900/
Note that due to the manner in which Arm develops IP and tracks errata,
some CPUs share a common erratum number and some CPUs have multiple
erratum numbers for the same HW issue.
On parts without SB, it is necessary to use ISB for the workaround. The
spec_bar() macro used in the mitigation will expand to a "DSB SY; ISB"
sequence in this case, which is sufficient on all affected parts.
Enable the existing mitigation by adding the relevant MIDRs to
erratum_spec_ssbs_list. The list is sorted alphanumerically (involving
moving Neoverse-V3 after Neoverse-V2) so that this is easy to audit and
potentially extend again in future. The Kconfig text is also updated to
clarify the set of affected parts and the mitigation.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240801101803.1982459-4-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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