On Tue, May 22, 2018 at 06:15:02PM +0100, Marc Zyngier wrote:

On 21/05/18 12:45, Russell King wrote:

quoted

+	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?

-- 
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