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SubjectRe: [PATCH v2 16/16] arm64: Add ARM_SMCCC_ARCH_WORKAROUND_1 BP hardening support
Hi Marc,

On 2018/1/30 1:45, Marc Zyngier wrote:
> static int enable_psci_bp_hardening(void *data)
> {
> const struct arm64_cpu_capabilities *entry = data;
> - if (psci_ops.get_version)
> + if (psci_ops.get_version) {
> + if (check_smccc_arch_workaround_1(entry))
> + return 0;

If I'm using the new version SMCCC, the firmware have the choice to decide
whether this machine needs the workaround, even if the CPU is vulnerable
for CVE-2017-5715, but..

> +
> install_bp_hardening_cb(entry,
> (bp_hardening_cb_t)psci_ops.get_version,
> __psci_hyp_bp_inval_start,
> __psci_hyp_bp_inval_end);

..the code above seems will enable get_psci_version() for CPU and will
trap to trust firmware even the new version of firmware didn't say
we need the workaround, did I understand it correctly?

I'm ask this because some platform will not expose to users to
take advantage of CVE-2017-5715, and we can use different firmware
to report we need such workaround or not, then use a single kernel
image for both vulnerable platforms and no vulnerable ones.


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