Re: [RFC PATCH] mm, oom: distinguish blockable mode for mmu notifiers

[Paolo Bonzini]

On 22/06/2018 17:02, Michal Hocko wrote:
> @@ -7215,6 +7216,8 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
>  	apic_address = gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
>  	if (start <= apic_address && apic_address < end)
>  		kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
> +
> +	return 0;

This is wrong, gfn_to_hva can sleep.

You could do the the kvm_make_all_cpus_request unconditionally, but only
if !blockable is a really rare thing.  OOM would be fine, since the
request actually would never be processed, but I'm afraid of more uses
of !blockable being introduced later.

Thanks,

Paolo