[PATCH v5 4/4] arm64: paravirt: Enable errata based on implementation CPUs
Oliver Upton
oliver.upton at linux.dev
Mon Jan 27 09:37:54 PST 2025
On Fri, Jan 24, 2025 at 03:17:32PM +0000, Shameer Kolothum wrote:
> +void __init pv_target_impl_cpu_init(void)
I get the sense that this implementation should actually be part of the
KVM guest services driver in drivers/firmware/smccc/kvm_guest.c
> +{
> + int i;
> + unsigned long max_cpus;
> + struct arm_smccc_res res;
> + const u32 funcs[] = {
> + ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_VER,
> + ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_CPUS,
> + };
> +
> + /* Check we have already set targets */
> + if (target_impl_cpu_num)
> + return;
> +
> + for (i = 0; i < ARRAY_SIZE(funcs); ++i) {
> + if (!kvm_arm_hyp_service_available(funcs[i]))
> + return;
> + }
nit: drop the for loop and just use the literal values.
> + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_DISCOVER_IMPL_VER_FUNC_ID,
> + 0, &res);
> + if (res.a0 != SMCCC_RET_SUCCESS)
> + return;
> +
> + if (res.a1 != ARM_SMCCC_KVM_DISCOVER_IMPL_VER_1_0 || !res.a2) {
This is brittle. The versioning scheme really should match that of PSCI
/ SMCCC, where minor revisions within the same major are backwards
compatible with older clients.
So consider just checking that the major version is 1.
> + pr_warn("Unsupported target impl version or CPU implementations\n");
This would be more useful if you provide context (i.e. the detected
version).
--
Thanks,
Oliver
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