On Mon, Dec 09, 2024 at 03:34:59PM -0800, Julius Werner wrote: > > > NOTE: presumably this patch won't actually do much on its own because > > > (I believe) it requires a firmware update to go with it. > > > > Why? is_spectre_bhb_fw_affected() returns true if (cpu in list OR fw > > mitigated) > > That affects reporting, but the mitigation works by making an > ARM_SMCCC_ARCH_WORKAROUND_3 Secure Monitor Call to firmware, and that > only works if that call is implemented in firmware. Trusted-Firmware-A > is currently the only open source firmware I'm aware of that > implements this call, and it only supports Kryo 4 and 6 upstream (not > 2 or 3). > > So in order for this patch to actually be able to do anything other > than report that the mitigation is missing, it would need to run on > devices that either use a downstream fork of TF-A with added Kryo 2/3 > support (I doubt this exists because AFAIK Kryo 4 was Qualcomm's first > attempt to use TF-A) or use some other proprietary kind of Secure > Monitor firmware that has this SMC and mitigation implemented > separately. (It seems unlikely that Qualcomm did this in their QTEE > firmware, since if they had they would have probably also added the > MIDRs here to Linux to activate it.) Ack, thanks for the detailed explanation. -- With best wishes Dmitry
