[PATCH 0/3] arm64: proton-pack: Add Spectre-BSE mitigation for Cortex-A7{2,3,5}

[Doebel, Bjoern]

Hi again James,

> Spectre-BSE is a variant of Spectre-BHB that abuses a power-saving mode
> on some older cores to dodge the BHB mitigation applied to the branch predictor.
> 
> Only A72r0 actually needs anything doing - this is basically a bug in the
> published BHB mitigation sequence that was published for A72r0. This
> series moves A72r0 to use the WA1 firmware call for mitigation, and adds
> the necessary reporting parts for user-space to discover which parts of
> BHB/BSE are mitigated or vulnerable.
> 
> WA1 is used instead of WA3 which was new for BHB because we can't rely
> on hypervisors not to use the 'local' workaround, and for Spectre-BSE
> we don't need to worry about discovery via. (Which is why WA3 exists -
> for cores not vulnerable to the issue mititaged by WA1).
> 
> Arm's description of this vulnerability can be found here:
> https://developer.arm.com/Arm%20Security%20Center/Spectre-BSE
> 
> This series is based on arm64/for-next/core, and can be retrieved from:
> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/log/?h=spectre_bse/v1
> 
> Backports of this version can also be found under spectre_bse/backports
> of the above repo.
> 
> Because this vulnerability is hard to expoit, but the cost of mitigating
> it is high - the mitigation is disabled by default. (see the last
> patch). To enable the mitigation, a command-line argument is needed:
> 'spectre_bse'.

I see that the patch to introduce this parameter is in the git series 
you linked above, but it is on top of the three patches in this series. 
Did you intend to send it as patch 4/4?

Best regards,
Bjoern