From: Sean Christopherson <seanjc@google.com>
To: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Igor Mammedov <imammedo@redhat.com>,
Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Huacai Chen <chenhuacai@kernel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
Paul Mackerras <paulus@ozlabs.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Janosch Frank <frankja@linux.ibm.com>,
David Hildenbrand <david@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Anup Patel <anup.patel@wdc.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Atish Patra <atish.patra@wdc.com>,
Ben Gardon <bgardon@google.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 26/29] KVM: Optimize gfn lookup in kvm_zap_gfn_range()
Date: Wed, 1 Dec 2021 16:36:30 +0000 [thread overview]
Message-ID: <Yaekjrr1OVrgwUic@google.com> (raw)
In-Reply-To: <7119b08c-e82a-8b81-7f9e-2e79f8276d51@maciej.szmigiero.name>
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.
static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
gfn_t start, gfn_t end)
{
struct kvm_memslot_iter iter;
kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
if (iter.slot->id != id)
return true;
}
return false;
}
vs.
static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
gfn_t start, gfn_t end)
{
struct kvm_memslot_iter iter;
kvm_for_each_memslot_in_gfn_range(&iter, slots, start, end) {
if (kvm_memslot_iter_slot(&iter)->id != id)
return true;
}
return false;
}
next prev parent reply other threads:[~2021-12-01 16:36 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-30 21:41 [PATCH v6 00/29] KVM: Scalable memslots implementation Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 01/29] KVM: Require total number of memslot pages to fit in an unsigned long Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 02/29] KVM: Open code kvm_delete_memslot() into its only caller Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 03/29] KVM: Resync only arch fields when slots_arch_lock gets reacquired Maciej S. Szmigiero
2021-12-01 1:07 ` Sean Christopherson
2021-12-01 15:45 ` Maciej S. Szmigiero
2021-12-02 10:32 ` Paolo Bonzini
2021-11-30 21:41 ` [PATCH v6 04/29] KVM: Use "new" memslot's address space ID instead of dedicated param Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 05/29] KVM: Let/force architectures to deal with arch specific memslot data Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 06/29] KVM: arm64: Use "new" memslot instead of userspace memory region Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 07/29] KVM: MIPS: Drop pr_debug from memslot commit to avoid using "mem" Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 08/29] KVM: PPC: Avoid referencing userspace memory region in memslot updates Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 09/29] KVM: s390: Use "new" memslot instead of userspace memory region Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 10/29] KVM: x86: " Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 11/29] KVM: RISC-V: " Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 12/29] KVM: Stop passing kvm_userspace_memory_region to arch memslot hooks Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 13/29] KVM: Use prepare/commit hooks to handle generic memslot metadata updates Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 14/29] KVM: x86: Don't assume old/new memslots are non-NULL at memslot commit Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 15/29] KVM: s390: Skip gfn/size sanity checks on memslot DELETE or FLAGS_ONLY Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 16/29] KVM: Don't make a full copy of the old memslot in __kvm_set_memory_region() Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 17/29] KVM: x86: Don't call kvm_mmu_change_mmu_pages() if the count hasn't changed Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 18/29] KVM: x86: Use nr_memslot_pages to avoid traversing the memslots array Maciej S. Szmigiero
2021-12-01 2:21 ` Sean Christopherson
2021-12-01 15:45 ` Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 19/29] KVM: Integrate gfn_to_memslot_approx() into search_memslots() Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 20/29] KVM: Move WARN on invalid memslot index to update_memslots() Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 21/29] KVM: Resolve memslot ID via a hash table instead of via a static array Maciej S. Szmigiero
2021-12-01 2:54 ` Sean Christopherson
2021-12-01 15:45 ` Maciej S. Szmigiero
2021-12-01 16:23 ` Sean Christopherson
2021-11-30 21:41 ` [PATCH v6 22/29] KVM: Use interval tree to do fast hva lookup in memslots Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 23/29] KVM: s390: Introduce kvm_s390_get_gfn_end() Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 24/29] KVM: Keep memslots in tree-based structures instead of array-based ones Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 25/29] KVM: Call kvm_arch_flush_shadow_memslot() on the old slot in kvm_invalidate_memslot() Maciej S. Szmigiero
2021-12-01 3:27 ` Sean Christopherson
2021-12-01 15:45 ` Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 26/29] KVM: Optimize gfn lookup in kvm_zap_gfn_range() Maciej S. Szmigiero
2021-12-01 3:41 ` Sean Christopherson
2021-12-01 15:45 ` Maciej S. Szmigiero
2021-12-01 16:36 ` Sean Christopherson [this message]
2021-12-01 23:08 ` Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 27/29] KVM: Optimize overlapping memslots check Maciej S. Szmigiero
2021-12-01 3:08 ` Sean Christopherson
2021-12-01 15:45 ` Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 28/29] KVM: Wait 'til the bitter end to initialize the "new" memslot Maciej S. Szmigiero
2021-11-30 21:41 ` [PATCH v6 29/29] KVM: Dynamically allocate "new" memslots from the get-go Maciej S. Szmigiero
2021-12-01 3:45 ` [PATCH v6 00/29] KVM: Scalable memslots implementation Sean Christopherson
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