From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: "Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, "Xiao Guangrong" <guangrong.xiao@gmail.com>
Subject: Re: [PATCH v2 11/27] KVM: x86/mmu: Zap only the relevant pages when removing a memslot
Date: Wed, 21 Aug 2019 13:30:41 -0700 [thread overview]
Message-ID: <20190821203041.GJ29345@linux.intel.com> (raw)
In-Reply-To: <20190821133504.79b87767@x1.home>
On Wed, Aug 21, 2019 at 01:35:04PM -0600, Alex Williamson wrote:
> On Wed, 21 Aug 2019 13:08:59 -0600
> Alex Williamson <alex.williamson@redhat.com> wrote:
> > Does this suggests something is still fundamentally wrong with the
> > premise of this change or have I done something stupid?
>
> Seems the latter, particularly your comment that we're looking for
> pages pointing to the gfn range to be removed, not just those in the
> range. Slot gfn ranges like ffe00-ffe1f are getting reduced to 0-0 or
> c0000-c0000, zapping zero or c0000, and I think one of the ones you
> were looking for c1080-c1083 is reduce to c1000-c1000 and therefore
> zaps sp->gfn c1000. I'll keep looking. Thanks,
Ya. As far as where to look, at this point I don't think it's an issue of
incorrect zapping. Not because I'm 100% confident the zapping logic is
correct, but because many of the tests, e.g. removing 'sp->gfn != gfn' and
not being able to exclude APIC/IOAPIC ranges, suggest that the badness is
'fixed' by zapping seemingly unrelated sps.
In other words, it may be fundamentally wrong to zap only the memslot
being removed, but I really want to know why. History isn't helpful as
KVM has always zapped all pages when removing a memslot (on x86), and the
introduction of the per-memslot flush hook in commit
2df72e9bc4c5 ("KVM: split kvm_arch_flush_shadow")
was all about refactoring generic code, and doesn't have any information
on whether per-memslot flushing was actually tried for x86.
next prev parent reply other threads:[~2019-08-21 20:30 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-05 20:54 [PATCH v2 00/27] KVM: x86/mmu: Remove fast invalidate mechanism Sean Christopherson
2019-02-05 20:54 ` [PATCH v2 01/27] KVM: Call kvm_arch_memslots_updated() before updating memslots Sean Christopherson
2019-02-06 9:12 ` Cornelia Huck
2019-02-12 12:36 ` [PATCH v2 00/27] KVM: x86/mmu: Remove fast invalidate mechanism Paolo Bonzini
[not found] ` <20190205210137.1377-11-sean.j.christopherson@intel.com>
2019-08-13 16:04 ` [PATCH v2 11/27] KVM: x86/mmu: Zap only the relevant pages when removing a memslot Alex Williamson
2019-08-13 17:04 ` Sean Christopherson
2019-08-13 17:57 ` Alex Williamson
2019-08-13 19:33 ` Alex Williamson
2019-08-13 20:19 ` Sean Christopherson
2019-08-13 20:37 ` Paolo Bonzini
2019-08-13 21:14 ` Alex Williamson
2019-08-13 21:15 ` Paolo Bonzini
2019-08-13 22:10 ` Alex Williamson
2019-08-15 14:46 ` Sean Christopherson
2019-08-15 15:23 ` Alex Williamson
2019-08-15 16:00 ` Sean Christopherson
2019-08-15 18:16 ` Alex Williamson
2019-08-15 19:25 ` Sean Christopherson
2019-08-15 20:11 ` Alex Williamson
2019-08-19 16:03 ` Paolo Bonzini
2019-08-20 20:03 ` Sean Christopherson
2019-08-20 20:42 ` Alex Williamson
2019-08-20 21:02 ` Sean Christopherson
2019-08-21 19:08 ` Alex Williamson
2019-08-21 19:35 ` Alex Williamson
2019-08-21 20:30 ` Sean Christopherson [this message]
2019-08-23 2:25 ` Sean Christopherson
2019-08-23 22:05 ` Alex Williamson
2019-08-21 20:10 ` Sean Christopherson
2019-08-26 7:36 ` Tian, Kevin
2019-08-26 14:56 ` Sean Christopherson
2020-06-26 17:32 ` Sean Christopherson
2022-10-20 18:31 ` Alexander Graf
2022-10-20 20:37 ` Sean Christopherson
2022-10-20 21:06 ` Alexander Graf
2022-10-21 19:40 ` Sean Christopherson
2022-10-24 6:12 ` Alexander Graf
2022-10-24 15:55 ` Sean Christopherson
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