BPI-R4 with Filogic 880 (Arm Cortex-A73): Spectre-BHB.

[Martin Schiller]

On 2025-03-05 14:48, Robert Marko wrote:
> On Wed, 5 Mar 2025 at 14:43, Martin Schiller <ms at dev.tdt.de> wrote:
>> 
>> CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY was disabled with commit
>> 6b007d2512ad (treewide: disable spectre mitigation on unaffected Arm64
>> targets) for all targets in target/linux/mediatek/filogic folder, but
>> the Arm Cortex-A73 in the Filogic 880 are affected [0].
>> 
>> So should we enable CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY for this
>> subtarget again?
> 
> If MT7988 is affected then yes.

Another option we maybe should activate is CONFIG_UNMAP_KERNEL_AT_EL0.

According to [0], the cortex a53 and a73 are not affected, but
mediatek/filogic and mediatek/mt7622 are the only arm64 subtargets where
this feature is disabled.

> 
>> 
>> On the other hand, the target.mk in this subtarget folder states it is
>> CPU_TYPE:=cortex-a53, which is not correct for all the supported 
>> systems
>> in this subtarget.
>> 
>> Do we have to split this subtarget into filogic830, filogic880, etc.?
> 
> This is intentionally done, as A73 core is backwards compatible with
> A53 instructions
> since it only adds on top of it, so to not introduce yet another
> package target A53 ones
> are reused.
> 
> Regards,
> Robert
>> 
>> Regards,
>> Martin
>> 
>> [0]
>> https://developer.arm.com/Arm%20Security%20Center/Speculative%20Processor%20Vulnerability
>> 
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