On Thu, Jul 29, 2021 at 11:40:06AM +0100, Shameer Kolothum wrote:
> A new VMID allocator for arm64 KVM use. This is based on
> arm64 ASID allocator algorithm.
>
> One major deviation from the ASID allocator is the way we
> flush the context. Unlike ASID allocator, we expect less
> frequent rollover in the case of VMIDs. Hence, instead of
> marking the CPU as flush_pending and issuing a local context
> invalidation on the next context switch, we broadcast TLB
> flush + I-cache invalidation over the inner shareable domain
> on rollover.
>
> Signed-off-by: Shameer Kolothum <[email protected]>
> ---
[...]
> +void kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
> +{
> + unsigned long flags;
> + unsigned int cpu;
> + u64 vmid, old_active_vmid;
> +
> + vmid = atomic64_read(&kvm_vmid->id);
> +
> + /*
> + * Please refer comments in check_and_switch_context() in
> + * arch/arm64/mm/context.c.
> + */
> + old_active_vmid = atomic64_read(this_cpu_ptr(&active_vmids));
> + if (old_active_vmid && vmid_gen_match(vmid) &&
> + atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_vmids),
> + old_active_vmid, vmid))
> + return;
> +
> + raw_spin_lock_irqsave(&cpu_vmid_lock, flags);
> +
> + /* Check that our VMID belongs to the current generation. */
> + vmid = atomic64_read(&kvm_vmid->id);
> + if (!vmid_gen_match(vmid)) {
> + vmid = new_vmid(kvm_vmid);
> + atomic64_set(&kvm_vmid->id, vmid);
new_vmid() can just set kvm_vmid->id directly
> + }
> +
> + cpu = smp_processor_id();
Why?
Will
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