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From: Ben Gardon <bgardon@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
	Cannon Matthews <cannonmatthews@google.com>,
	Peter Xu <peterx@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Peter Shier <pshier@google.com>,
	Peter Feiner <pfeiner@google.com>,
	Junaid Shahid <junaids@google.com>,
	Jim Mattson <jmattson@google.com>,
	Yulei Zhang <yulei.kernel@gmail.com>,
	Wanpeng Li <kernellwp@gmail.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>
Subject: Re: [PATCH 18/22] kvm: mmu: Support disabling dirty logging for the tdp MMU
Date: Wed, 7 Oct 2020 10:28:29 -0700	[thread overview]
Message-ID: <CANgfPd8Nzi2Cb3cvh5nFoaXTPbfm7Y77e4iM6-zOp5Qa3wNJBw@mail.gmail.com> (raw)
In-Reply-To: <5dc72eec-a4bd-f31a-f439-cdf8c5b48c05@redhat.com>

On Wed, Oct 7, 2020 at 10:21 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 07/10/20 18:30, Ben Gardon wrote:
> >> I'm starting to wonder if another iterator like
> >> for_each_tdp_leaf_pte_root would be clearer, since this idiom repeats
> >> itself quite often.  The tdp_iter_next_leaf function would be easily
> >> implemented as
> >>
> >>         while (likely(iter->valid) &&
> >>                (!is_shadow_present_pte(iter.old_spte) ||
> >>                 is_last_spte(iter.old_spte, iter.level))
> >>                 tdp_iter_next(iter);
> > Do you see a substantial efficiency difference between adding a
> > tdp_iter_next_leaf and building on for_each_tdp_pte_using_root with
> > something like:
> >
> > #define for_each_tdp_leaf_pte_using_root(_iter, _root, _start, _end)    \
> >         for_each_tdp_pte_using_root(_iter, _root, _start, _end)         \
> >                 if (!is_shadow_present_pte(_iter.old_spte) ||           \
> >                     !is_last_spte(_iter.old_spte, _iter.level))         \
> >                         continue;                                       \
> >                 else
> >
> > I agree that putting those checks in a wrapper makes the code more concise.
> >
>
> No, that would be just another way to write the same thing.  That said,
> making the iteration API more complicated also has disadvantages because
> if get a Cartesian explosion of changes.

I wouldn't be too worried about that. The only things I ever found
worth making an iterator case for were:
Every SPTE
Every present SPTE
Every present leaf SPTE

And really there aren't many cases that use the middle one.

>
> Regarding the naming, I'm leaning towards
>
>     tdp_root_for_each_pte
>     tdp_vcpu_for_each_pte
>
> which is shorter than the version with "using" and still clarifies that
> "root" and "vcpu" are the thing that the iteration works on.

That sounds good to me. I agree it's similarly clear.

>
> Paolo
>

  reply	other threads:[~2020-10-07 17:28 UTC|newest]

Thread overview: 105+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-25 21:22 [PATCH 00/22] Introduce the TDP MMU Ben Gardon
2020-09-25 21:22 ` [PATCH 01/22] kvm: mmu: Separate making SPTEs from set_spte Ben Gardon
2020-09-30  4:55   ` Sean Christopherson
2020-09-30 23:03     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 02/22] kvm: mmu: Introduce tdp_iter Ben Gardon
2020-09-26  0:04   ` Paolo Bonzini
2020-09-30  5:06     ` Sean Christopherson
2020-09-26  0:54   ` Paolo Bonzini
2020-09-30  5:08   ` Sean Christopherson
2020-09-30  5:24   ` Sean Christopherson
2020-09-30  6:24     ` Paolo Bonzini
2020-09-30 23:20   ` Eric van Tassell
2020-09-30 23:34     ` Paolo Bonzini
2020-10-01  0:07       ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 03/22] kvm: mmu: Init / Uninit the TDP MMU Ben Gardon
2020-09-26  0:06   ` Paolo Bonzini
2020-09-30  5:34   ` Sean Christopherson
2020-09-30 18:36     ` Ben Gardon
2020-09-30 16:57   ` Sean Christopherson
2020-09-30 17:39     ` Paolo Bonzini
2020-09-30 18:42       ` Ben Gardon
2020-09-25 21:22 ` [PATCH 04/22] kvm: mmu: Allocate and free TDP MMU roots Ben Gardon
2020-09-30  6:06   ` Sean Christopherson
2020-09-30  6:26     ` Paolo Bonzini
2020-09-30 15:38       ` Sean Christopherson
2020-10-12 22:59     ` Ben Gardon
2020-10-12 23:59       ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 05/22] kvm: mmu: Add functions to handle changed TDP SPTEs Ben Gardon
2020-09-26  0:39   ` Paolo Bonzini
2020-09-28 17:23     ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 06/22] kvm: mmu: Make address space ID a property of memslots Ben Gardon
2020-09-30  6:10   ` Sean Christopherson
2020-09-30 23:11     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 07/22] kvm: mmu: Support zapping SPTEs in the TDP MMU Ben Gardon
2020-09-26  0:14   ` Paolo Bonzini
2020-09-30  6:15   ` Sean Christopherson
2020-09-30  6:28     ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 08/22] kvm: mmu: Separate making non-leaf sptes from link_shadow_page Ben Gardon
2020-09-25 21:22 ` [PATCH 09/22] kvm: mmu: Remove disallowed_hugepage_adjust shadow_walk_iterator arg Ben Gardon
2020-09-30 16:19   ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 10/22] kvm: mmu: Add TDP MMU PF handler Ben Gardon
2020-09-26  0:24   ` Paolo Bonzini
2020-09-30 16:37   ` Sean Christopherson
2020-09-30 16:55     ` Paolo Bonzini
2020-09-30 17:37     ` Paolo Bonzini
2020-10-06 22:35       ` Ben Gardon
2020-10-06 22:33     ` Ben Gardon
2020-10-07 20:55       ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 11/22] kvm: mmu: Factor out allocating a new tdp_mmu_page Ben Gardon
2020-09-26  0:22   ` Paolo Bonzini
2020-09-30 18:53     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 12/22] kvm: mmu: Allocate struct kvm_mmu_pages for all pages in TDP MMU Ben Gardon
2020-09-25 21:22 ` [PATCH 13/22] kvm: mmu: Support invalidate range MMU notifier for " Ben Gardon
2020-09-30 17:03   ` Sean Christopherson
2020-09-30 23:15     ` Ben Gardon
2020-09-30 23:24       ` Sean Christopherson
2020-09-30 23:27         ` Ben Gardon
2020-09-25 21:22 ` [PATCH 14/22] kvm: mmu: Add access tracking for tdp_mmu Ben Gardon
2020-09-26  0:32   ` Paolo Bonzini
2020-09-30 17:48   ` Sean Christopherson
2020-10-06 23:38     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 15/22] kvm: mmu: Support changed pte notifier in tdp MMU Ben Gardon
2020-09-26  0:33   ` Paolo Bonzini
2020-09-28 15:11   ` Paolo Bonzini
2020-10-07 16:53     ` Ben Gardon
2020-10-07 17:18       ` Paolo Bonzini
2020-10-07 17:30         ` Ben Gardon
2020-10-07 17:54           ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 16/22] kvm: mmu: Add dirty logging handler for changed sptes Ben Gardon
2020-09-26  0:45   ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 17/22] kvm: mmu: Support dirty logging for the TDP MMU Ben Gardon
2020-09-26  1:04   ` Paolo Bonzini
2020-10-08 18:27     ` Ben Gardon
2020-09-29 15:07   ` Paolo Bonzini
2020-09-30 18:04   ` Sean Christopherson
2020-09-30 18:08     ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 18/22] kvm: mmu: Support disabling dirty logging for the tdp MMU Ben Gardon
2020-09-26  1:09   ` Paolo Bonzini
2020-10-07 16:30     ` Ben Gardon
2020-10-07 17:21       ` Paolo Bonzini
2020-10-07 17:28         ` Ben Gardon [this message]
2020-10-07 17:53           ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 19/22] kvm: mmu: Support write protection for nesting in " Ben Gardon
2020-09-30 18:06   ` Sean Christopherson
2020-09-25 21:23 ` [PATCH 20/22] kvm: mmu: NX largepage recovery for TDP MMU Ben Gardon
2020-09-26  1:14   ` Paolo Bonzini
2020-09-30 22:23     ` Ben Gardon
2020-09-29 18:24   ` Paolo Bonzini
2020-09-30 18:15   ` Sean Christopherson
2020-09-30 19:56     ` Paolo Bonzini
2020-09-30 22:33       ` Ben Gardon
2020-09-30 22:27     ` Ben Gardon
2020-09-25 21:23 ` [PATCH 21/22] kvm: mmu: Support MMIO in the " Ben Gardon
2020-09-30 18:19   ` Sean Christopherson
2020-09-25 21:23 ` [PATCH 22/22] kvm: mmu: Don't clear write flooding count for direct roots Ben Gardon
2020-09-26  1:25   ` Paolo Bonzini
2020-10-05 22:48     ` Ben Gardon
2020-10-05 23:44       ` Sean Christopherson
2020-10-06 16:19         ` Ben Gardon
2020-09-26  1:14 ` [PATCH 00/22] Introduce the TDP MMU Paolo Bonzini
2020-09-28 17:31 ` Paolo Bonzini
2020-09-29 17:40   ` Ben Gardon
2020-09-29 18:10     ` Paolo Bonzini
2020-09-30  6:19 ` Sean Christopherson
2020-09-30  6:30   ` Paolo Bonzini

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