From: Christoffer Dall <christoffer.dall@linaro.org>
To: Mario Smarduch <m.smarduch@samsung.com>
Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Subject: Re: huge 2nd stage pages and live migration
Date: Fri, 28 Mar 2014 12:17:36 -0700 [thread overview]
Message-ID: <20140328191736.GK25519@cbox> (raw)
In-Reply-To: <5335B3CD.30207@samsung.com>
On Fri, Mar 28, 2014 at 10:39:25AM -0700, Mario Smarduch wrote:
> Hello
>
> I've been working on live migration for ARM-KVM, and noticed
> problem completing migration with huge 2nd stage tables.
>
>
> Aafter write protecting the VM, for write fault 512 page bits
> are set in dirty_bitmap[] to take into account future writes to
> huge page.The pmd is write protected again when QEMU reads the
> dirty log, and the cycle repeats. With this not even a idle
> 32MB VM completes live migration.
>
> If QEMU uses THPs, and 2nd stage tables use pte's, then there
> is no problem, live migration is quick. I'm assumung QEMU and Guest
> huge pages with 2nd stage page table pte's should work fine too.
>
> I'm wondering how this has been solved (for any architecture)?
>
I don't know if there's a generic solution (have you looked at x86/PPC
what they do?), but I don't see any conceptual problem with putting the
VM into use-pte-for-2nd-stage-mappings-I'm-migrating-mode.
-Christoffer
prev parent reply other threads:[~2014-03-28 19:17 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-28 17:39 huge 2nd stage pages and live migration Mario Smarduch
2014-03-28 19:17 ` Christoffer Dall [this message]
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