LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Andrea Arcangeli <andrea@qumranet.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <clameter@sgi.com>, Robin Holt <holt@sgi.com>,
	Avi Kivity <avi@qumranet.com>, Izik Eidus <izike@qumranet.com>,
	kvm-devel@lists.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	general@lists.openfabrics.org,
	Steve Wise <swise@opengridcomputing.com>,
	Roland Dreier <rdreier@cisco.com>,
	Kanoj Sarcar <kanojsarcar@yahoo.com>,
	steiner@sgi.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, daniel.blueman@quadrics.com
Subject: Re: [PATCH] KVM swapping with MMU Notifiers V7
Date: Mon, 18 Feb 2008 13:17:15 +0100	[thread overview]
Message-ID: <20080218121715.GR11732@v2.random> (raw)
In-Reply-To: <20080216030817.965ff1f7.akpm@linux-foundation.org>

On Sat, Feb 16, 2008 at 03:08:17AM -0800, Andrew Morton wrote:
> On Sat, 16 Feb 2008 11:48:27 +0100 Andrea Arcangeli <andrea@qumranet.com> wrote:
> 
> > +void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
> > +					   struct mm_struct *mm,
> > +					   unsigned long start, unsigned long end,
> > +					   int lock)
> > +{
> > +	for (; start < end; start += PAGE_SIZE)
> > +		kvm_mmu_notifier_invalidate_page(mn, mm, start);
> > +}
> > +
> > +static const struct mmu_notifier_ops kvm_mmu_notifier_ops = {
> > +	.invalidate_page	= kvm_mmu_notifier_invalidate_page,
> > +	.age_page		= kvm_mmu_notifier_age_page,
> > +	.invalidate_range_end	= kvm_mmu_notifier_invalidate_range_end,
> > +};
> 
> So this doesn't implement ->invalidate_range_start().

Correct. range_start is needed by subsystems that don't pin the pages
(so they've to drop the secondary mmu mappings on the physical page
before the page is released by the linux VM).

> By what means does it prevent new mappings from being established in the
> range after core mm has tried to call ->invalidate_rande_start()?
> mmap_sem, I assume?

No, populate range only takes the mmap_sem in read mode and the kvm page
fault also is of course taking it only in read mode.

What makes it safe, is that invalidate_range_end is called _after_ the
linux pte is clear. The kvm page fault, if it triggers, it will call
into get_user_pages again to re-establish the linux pte _before_
establishing the spte.

It's the same reason why it's safe to flush the tlb after clearing the
linux pte. sptes are like a secondary tlb.

> > +			/* set userspace_addr atomically for kvm_hva_to_rmapp */
> > +			spin_lock(&kvm->mmu_lock);
> > +			memslot->userspace_addr = userspace_addr;
> > +			spin_unlock(&kvm->mmu_lock);
> 
> are you sure?  kvm_unmap_hva() and kvm_age_hva() read ->userspace_addr a
> single time and it doesn't immediately look like there's a need to take the
> lock here?

gcc will always write it with a movq but this is to be
C-specs-compliant and because this is by far not a performance
critical path I thought it was simpler than some other atomic move in
a single insn.

  reply	other threads:[~2008-02-18 12:17 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-15  6:48 [patch 0/6] " Christoph Lameter
2008-02-15  6:49 ` [patch 1/6] mmu_notifier: Core code Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16  8:45     ` Avi Kivity
2008-02-16  8:56       ` Andrew Morton
2008-02-16  9:21         ` Avi Kivity
2008-02-16 10:41     ` Brice Goglin
2008-02-16 10:58       ` Andrew Morton
2008-02-16 19:31         ` Christoph Lameter
2008-02-16 19:21     ` Christoph Lameter
2008-02-17  3:01       ` Andrea Arcangeli
2008-02-17 12:24         ` Robin Holt
2008-02-17  5:04     ` Doug Maxey
2008-02-18 22:33   ` Roland Dreier
2008-02-15  6:49 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16 19:26     ` Christoph Lameter
2008-02-19  8:54   ` Nick Piggin
2008-02-19 13:34     ` Andrea Arcangeli
2008-02-27 22:23       ` Christoph Lameter
2008-02-27 23:57         ` Andrea Arcangeli
2008-02-19 23:08   ` Nick Piggin
2008-02-20  1:00     ` Andrea Arcangeli
2008-02-20  3:00       ` Robin Holt
2008-02-20  3:11         ` Nick Piggin
2008-02-20  3:19           ` Robin Holt
2008-02-27 22:39       ` Christoph Lameter
2008-02-28  0:38         ` Andrea Arcangeli
2008-02-27 22:35     ` Christoph Lameter
2008-02-27 22:42       ` Jack Steiner
2008-02-28  0:10       ` Christoph Lameter
2008-02-28  0:11       ` Andrea Arcangeli
2008-02-28  0:14         ` Christoph Lameter
2008-02-28  0:52           ` Andrea Arcangeli
2008-02-28  1:03             ` Christoph Lameter
2008-02-28  1:10               ` Andrea Arcangeli
2008-02-28 18:43                 ` Christoph Lameter
2008-02-29  0:55                   ` Andrea Arcangeli
2008-02-29  0:59                     ` Christoph Lameter
2008-02-29 13:13                       ` Andrea Arcangeli
2008-02-29 19:55                         ` Christoph Lameter
2008-02-29 20:17                           ` Andrea Arcangeli
2008-02-29 21:03                             ` Christoph Lameter
2008-02-29 21:23                               ` Andrea Arcangeli
2008-02-29 21:29                                 ` Christoph Lameter
2008-02-29 21:34                                 ` Christoph Lameter
2008-02-29 21:48                                   ` Andrea Arcangeli
2008-02-29 22:12                                     ` Christoph Lameter
2008-02-29 22:41                                       ` Andrea Arcangeli
2008-02-28 10:53             ` Robin Holt
2008-03-03  5:11       ` Nick Piggin
2008-03-03 19:28         ` Christoph Lameter
2008-03-03 19:50           ` Nick Piggin
2008-03-04 18:58             ` Christoph Lameter
2008-03-05  0:52               ` Nick Piggin
2008-02-15  6:49 ` [patch 3/6] mmu_notifier: invalidate_page callbacks Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16 11:07     ` Andrea Arcangeli
2008-02-16 19:22     ` Christoph Lameter
2008-02-16 19:54       ` Avi Kivity
2008-02-19  8:46       ` Nick Piggin
2008-02-19 13:30         ` Andrea Arcangeli
2008-02-18  1:51     ` Nick Piggin
2008-02-15  6:49 ` [patch 4/6] mmu_notifier: Skeleton driver for a simple mmu_notifier Christoph Lameter
2008-02-15  6:49 ` [patch 5/6] mmu_notifier: Support for drivers with revers maps (f.e. for XPmem) Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16 19:28     ` Christoph Lameter
2008-02-19 23:55   ` Nick Piggin
2008-02-20  3:12     ` Robin Holt
2008-02-20  3:51       ` Nick Piggin
2008-02-20  9:00         ` Robin Holt
2008-02-20  9:05           ` Robin Holt
2008-02-21  4:20           ` Nick Piggin
2008-02-21 10:58             ` Robin Holt
2008-02-26  6:11               ` Nick Piggin
2008-02-26  7:21                 ` [ofa-general] " Gleb Natapov
2008-02-26  8:52                   ` Nick Piggin
2008-02-26  9:38                     ` Gleb Natapov
2008-02-26  9:52                       ` KOSAKI Motohiro
2008-02-26 12:28                     ` Robin Holt
2008-02-26 12:29                 ` Robin Holt
2008-02-27 22:43     ` Christoph Lameter
2008-02-28  0:42       ` Andrea Arcangeli
2008-02-28  1:01         ` Christoph Lameter
2008-02-15  6:49 ` [patch 6/6] mmu_rmap_notifier: Skeleton for complex driver that uses its own rmaps Christoph Lameter
2008-02-16 10:48 ` [PATCH] KVM swapping with MMU Notifiers V7 Andrea Arcangeli
2008-02-16 11:08   ` Andrew Morton
2008-02-18 12:17     ` Andrea Arcangeli [this message]
2008-02-16 11:51   ` Robin Holt
2008-02-18 12:35     ` Andrea Arcangeli
2008-02-19  8:43 [patch] my mmu notifiers Nick Piggin
2008-02-19 13:58 ` Andrea Arcangeli
2008-02-19 23:11   ` Nick Piggin
2008-02-20  1:09     ` Andrea Arcangeli
2008-02-20 10:39       ` [PATCH] mmu notifiers #v6 Andrea Arcangeli
2008-02-20 10:45         ` [PATCH] KVM swapping (+ seqlock fix) with " Andrea Arcangeli
2008-02-27 22:06           ` [PATCH] KVM swapping with mmu notifiers #v7 Andrea Arcangeli
2008-02-28  8:42             ` izik eidus

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080218121715.GR11732@v2.random \
    --to=andrea@qumranet.com \
    --cc=a.p.zijlstra@chello.nl \
    --cc=akpm@linux-foundation.org \
    --cc=avi@qumranet.com \
    --cc=clameter@sgi.com \
    --cc=daniel.blueman@quadrics.com \
    --cc=general@lists.openfabrics.org \
    --cc=holt@sgi.com \
    --cc=izike@qumranet.com \
    --cc=kanojsarcar@yahoo.com \
    --cc=kvm-devel@lists.sourceforge.net \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=rdreier@cisco.com \
    --cc=steiner@sgi.com \
    --cc=swise@opengridcomputing.com \
    --subject='Re: [PATCH] KVM swapping with MMU Notifiers V7' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).