Messages in this thread | | | From | "Maciej S. Szmigiero" <> | Subject | Re: [PATCH v6 26/29] KVM: Optimize gfn lookup in kvm_zap_gfn_range() | Date | Thu, 2 Dec 2021 00:08:31 +0100 |
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On 01.12.2021 17:36, Sean Christopherson wrote: > On Wed, Dec 01, 2021, Maciej S. Szmigiero wrote: >> On 01.12.2021 04:41, Sean Christopherson wrote: >>> On Tue, Nov 30, 2021, Maciej S. Szmigiero wrote: >>>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h >>>> index 41efe53cf150..6fce6eb797a7 100644 >>>> --- a/include/linux/kvm_host.h >>>> +++ b/include/linux/kvm_host.h >>>> @@ -848,6 +848,105 @@ struct kvm_memory_slot *id_to_memslot(struct kvm_memslots *slots, int id) >>>> return NULL; >>>> } >>>> +/* Iterator used for walking memslots that overlap a gfn range. */ >>>> +struct kvm_memslot_iter { >>>> + struct kvm_memslots *slots; >>>> + gfn_t end; >>>> + struct rb_node *node; >>>> +}; >>> >>> ... >>> >>>> +static inline struct kvm_memory_slot *kvm_memslot_iter_slot(struct kvm_memslot_iter *iter) >>>> +{ >>>> + return container_of(iter->node, struct kvm_memory_slot, gfn_node[iter->slots->node_idx]); >>> >>> Having to use a helper in callers of kvm_for_each_memslot_in_gfn_range() is a bit >>> ugly, any reason not to grab @slot as well? Then the callers just do iter.slot, >>> which IMO is much more readable. >> >> "slot" can be easily calculated from "node" together with either "slots" or >> "node_idx" (the code above just adjusts a pointer) so storing it in the >> iterator makes little sense if the later are already stored there. > > I don't want the callers to have to calculate the slot. It's mostly syntatic > sugar, but I really do think it improves readability. And since the first thing > every caller will do is retrieve the slot, I see no benefit in forcing the caller > to do the work. > > E.g. in the simple kvm_check_memslot_overlap() usage, iter.slot->id is intuitive > and easy to parse, whereas kvm_memslot_iter_slot(&iter)->id is slightly more > difficult to parse and raises questions about why a function call is necessary > and what the function might be doing.
Personally, I don't think it's that much less readable, but I will change the code to store "slots" instead (as you wish) since it's the last remaining change - other than Paolo's call whether we should keep or drop the kvm_arch_flush_shadow_memslot()-related patch 25.
Thanks, Maciej
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