From: Ben Gardon <bgardon@google.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Peter Feiner <pfeiner@google.com>,
Peter Shier <pshier@google.com>,
Junaid Shahid <junaids@google.com>,
Jim Mattson <jmattson@google.com>
Subject: Re: [RFC PATCH 00/28] kvm: mmu: Rework the x86 TDP direct mapped case
Date: Fri, 6 Dec 2019 11:55:42 -0800 [thread overview]
Message-ID: <CANgfPd-XR0ZpbTtV21KrM_Ud1d0ntHxE6M4JzcFVZ4M0zG8XYQ@mail.gmail.com> (raw)
In-Reply-To: <20191127190922.GH22227@linux.intel.com>
I'm finally back in the office. Sorry for not getting back to you sooner.
I don't think it would be easy to send the synchronization changes
first. The reason they seem so small is that they're all handled by
the iterator. If we tried to put the synchronization changes in
without the iterator we'd have to 1.) deal with struct kvm_mmu_pages,
2.) deal with the rmap, and 3.) change a huge amount of code to insert
the synchronization changes into the existing framework. The changes
wouldn't be mechanical or easy to insert either since a lot of
bookkeeping is currently done before PTEs are updated, with no
facility for rolling back the bookkeeping on PTE cmpxchg failure. We
could start with the iterator changes and then do the synchronization
changes, but the other way around would be very difficult.
On Wed, Nov 27, 2019 at 11:09 AM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> On Thu, Sep 26, 2019 at 04:17:56PM -0700, Ben Gardon wrote:
> > The goal of this RFC is to demonstrate and gather feedback on the
> > iterator pattern, the memory savings it enables for the "direct case"
> > and the changes to the synchronization model. Though they are interwoven
> > in this series, I will separate the iterator from the synchronization
> > changes in a future series. I recognize that some feature work will be
> > needed to make this patch set ready for merging. That work is detailed
> > at the end of this cover letter.
>
> How difficult would it be to send the synchronization changes as a separate
> series in the not-too-distant future? At a brief glance, those changes
> appear to be tiny relative to the direct iterator changes. From a stability
> perspective, it would be nice if the locking changes can get upstreamed and
> tested in the wild for a few kernel versions before the iterator code is
> introduced.
next prev parent reply other threads:[~2019-12-06 19:55 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-26 23:17 [RFC PATCH 00/28] kvm: mmu: Rework the x86 TDP direct mapped case Ben Gardon
2019-09-26 23:17 ` [RFC PATCH 01/28] kvm: mmu: Separate generating and setting mmio ptes Ben Gardon
2019-11-27 18:15 ` Sean Christopherson
2019-09-26 23:17 ` [RFC PATCH 02/28] kvm: mmu: Separate pte generation from set_spte Ben Gardon
2019-11-27 18:25 ` Sean Christopherson
2019-09-26 23:17 ` [RFC PATCH 03/28] kvm: mmu: Zero page cache memory at allocation time Ben Gardon
2019-11-27 18:32 ` Sean Christopherson
2019-09-26 23:18 ` [RFC PATCH 04/28] kvm: mmu: Update the lpages stat atomically Ben Gardon
2019-11-27 18:39 ` Sean Christopherson
2019-12-06 20:10 ` Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 05/28] sched: Add cond_resched_rwlock Ben Gardon
2019-11-27 18:42 ` Sean Christopherson
2019-12-06 20:12 ` Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 06/28] kvm: mmu: Replace mmu_lock with a read/write lock Ben Gardon
2019-11-27 18:47 ` Sean Christopherson
2019-12-02 22:45 ` Sean Christopherson
2019-09-26 23:18 ` [RFC PATCH 07/28] kvm: mmu: Add functions for handling changed PTEs Ben Gardon
2019-11-27 19:04 ` Sean Christopherson
2019-09-26 23:18 ` [RFC PATCH 08/28] kvm: mmu: Init / Uninit the direct MMU Ben Gardon
2019-12-02 23:40 ` Sean Christopherson
2019-12-06 20:25 ` Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 09/28] kvm: mmu: Free direct MMU page table memory in an RCU callback Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 10/28] kvm: mmu: Flush TLBs before freeing direct MMU page table memory Ben Gardon
2019-12-02 23:46 ` Sean Christopherson
2019-12-06 20:31 ` Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 11/28] kvm: mmu: Optimize for freeing direct MMU PTs on teardown Ben Gardon
2019-12-02 23:54 ` Sean Christopherson
2019-09-26 23:18 ` [RFC PATCH 12/28] kvm: mmu: Set tlbs_dirty atomically Ben Gardon
2019-12-03 0:13 ` Sean Christopherson
2019-09-26 23:18 ` [RFC PATCH 13/28] kvm: mmu: Add an iterator for concurrent paging structure walks Ben Gardon
2019-12-03 2:15 ` Sean Christopherson
2019-12-18 18:25 ` Ben Gardon
2019-12-18 19:14 ` Sean Christopherson
2019-09-26 23:18 ` [RFC PATCH 14/28] kvm: mmu: Batch updates to the direct mmu disconnected list Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 15/28] kvm: mmu: Support invalidate_zap_all_pages Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 16/28] kvm: mmu: Add direct MMU page fault handler Ben Gardon
2020-01-08 17:20 ` Peter Xu
2020-01-08 18:15 ` Ben Gardon
2020-01-08 19:00 ` Peter Xu
2019-09-26 23:18 ` [RFC PATCH 17/28] kvm: mmu: Add direct MMU fast " Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 18/28] kvm: mmu: Add an hva range iterator for memslot GFNs Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 19/28] kvm: mmu: Make address space ID a property of memslots Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 20/28] kvm: mmu: Implement the invalidation MMU notifiers for the direct MMU Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 21/28] kvm: mmu: Integrate the direct mmu with the changed pte notifier Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 22/28] kvm: mmu: Implement access tracking for the direct MMU Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 23/28] kvm: mmu: Make mark_page_dirty_in_slot usable from outside kvm_main Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 24/28] kvm: mmu: Support dirty logging in the direct MMU Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 25/28] kvm: mmu: Support kvm_zap_gfn_range " Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 26/28] kvm: mmu: Integrate direct MMU with nesting Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 27/28] kvm: mmu: Lazily allocate rmap when direct MMU is enabled Ben Gardon
2019-09-26 23:18 ` [RFC PATCH 28/28] kvm: mmu: Support MMIO in the direct MMU Ben Gardon
2019-10-17 18:50 ` [RFC PATCH 00/28] kvm: mmu: Rework the x86 TDP direct mapped case Sean Christopherson
2019-10-18 13:42 ` Paolo Bonzini
2019-11-27 19:09 ` Sean Christopherson
2019-12-06 19:55 ` Ben Gardon [this message]
2019-12-06 19:57 ` Sean Christopherson
2019-12-06 20:42 ` Ben Gardon
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