On Tue, May 22, 2018 at 06:15:02PM +0100, Marc Zyngier wrote:
> On 21/05/18 12:45, Russell King wrote:
> > + switch (read_cpuid_part()) {
> > + case ARM_CPU_PART_CORTEX_A8:
> > + case ARM_CPU_PART_CORTEX_A9:
> > + case ARM_CPU_PART_CORTEX_A12:
> > + case ARM_CPU_PART_CORTEX_A17:
> > + case ARM_CPU_PART_CORTEX_A73:
> > + case ARM_CPU_PART_CORTEX_A75:
> > + harden_branch_predictor = harden_branch_predictor_bpiall;
> > + spectre_v2_method = "BPIALL";
> > + break;
>
> You don't seem to take into account the PFR0.CSV2 field which indicates
> that the CPU has a branch predictor that is immune to Spectre-v2.
That information is not covered in the description of the vulnerability
- the published information on the security-updates site states that
BPIALL is required without stating any conditions.
> See for example the Cortex-A75 r3p0 TRM[1].
So which cores should such a test be applied to? As I mention,
the support site doesn't give this detail. That brings up the
obvious question: what else does the web page miss out on?
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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