From: Avi Kivity <avi@redhat.com>
To: Scott Wood <scottwood@freescale.com>
Cc: Alexander Graf <agraf@suse.de>,
Anthony Liguori <anthony@codemonkey.ws>,
KVM list <kvm@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
qemu-devel <qemu-devel@nongnu.org>,
kvm-ppc <kvm-ppc@vger.kernel.org>
Subject: Re: [Qemu-devel] [RFC] Next gen kvm api
Date: Sat, 18 Feb 2012 11:49:27 +0200 [thread overview]
Message-ID: <4F3F7427.6020705@redhat.com> (raw)
In-Reply-To: <4F3D6A0E.4080705@freescale.com>
On 02/16/2012 10:41 PM, Scott Wood wrote:
> >>> Sharing the data structures is not need. Simply synchronize them before
> >>> lookup, like we do for ordinary registers.
> >>
> >> Ordinary registers are a few bytes. We're talking of dozens of kbytes here.
> >
> > A TLB way is a few dozen bytes, no?
>
> I think you mean a TLB set...
Yes, thanks.
> but the TLB (or part of it) may be fully
> associative.
A fully associative TLB has to be very small.
> On e500mc, it's 24 bytes for one TLB entry, and you'd need 4 entries for
> a set of TLB0, and all 64 entries in TLB1. So 1632 bytes total.
Syncing this every time you need a translation (for gdb or the monitor)
is trivial in terms of performance.
> Then we'd need to deal with tracking whether we synchronized one or more
> specific sets, or everything (for migration or debug TLB dump). The
> request to synchronize would have to come from within the QEMU MMU code,
> since that's the point where we know what to ask for (unless we
> duplicate the logic elsewhere). I'm not sure that reusing the standard
> QEMU MMU code for individual debug address translation is really
> simplifying things...
>
> And yes, we do have fancier hardware coming fairly soon for which this
> breaks (TLB0 entries can be loaded without host involvement, as long as
> there's a translation from guest physical to physical in a separate
> hardware table). It'd be reasonable to ignore TLB0 for migration (treat
> it as invalidated), but not for debug since that may be where the
> translation we're interested in resides.
>
So with this new hardware, the always-sync API breaks.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2012-02-18 9:49 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-02 16:09 [RFC] Next gen kvm api Avi Kivity
[not found] ` <CAB9FdM9M2DWXBxxyG-ez_5igT61x5b7ptw+fKfgaqMBU_JS5aA@mail.gmail.com>
2012-02-02 22:16 ` [Qemu-devel] " Rob Earhart
2012-02-05 13:14 ` Avi Kivity
2012-02-06 17:41 ` Rob Earhart
2012-02-06 19:11 ` Anthony Liguori
2012-02-07 12:03 ` Avi Kivity
2012-02-07 15:17 ` Anthony Liguori
2012-02-07 16:02 ` Avi Kivity
2012-02-07 16:18 ` Jan Kiszka
2012-02-07 16:21 ` Anthony Liguori
2012-02-07 16:29 ` Jan Kiszka
2012-02-15 13:41 ` Avi Kivity
2012-02-07 16:19 ` Anthony Liguori
2012-02-15 13:47 ` Avi Kivity
2012-02-07 12:01 ` Avi Kivity
2012-02-03 2:09 ` Anthony Liguori
2012-02-04 2:08 ` Takuya Yoshikawa
2012-02-22 13:06 ` Peter Zijlstra
2012-02-05 9:24 ` Avi Kivity
2012-02-07 1:08 ` Alexander Graf
2012-02-07 12:24 ` Avi Kivity
2012-02-07 12:51 ` Alexander Graf
2012-02-07 13:16 ` Avi Kivity
2012-02-07 13:40 ` Alexander Graf
2012-02-07 14:21 ` Avi Kivity
2012-02-07 14:39 ` Alexander Graf
2012-02-15 11:18 ` Avi Kivity
2012-02-15 11:57 ` Alexander Graf
2012-02-15 13:29 ` Avi Kivity
2012-02-15 13:37 ` Alexander Graf
2012-02-15 13:57 ` Avi Kivity
2012-02-15 14:08 ` Alexander Graf
2012-02-16 19:24 ` Avi Kivity
2012-02-16 19:34 ` Alexander Graf
2012-02-16 19:38 ` Avi Kivity
2012-02-16 20:41 ` Scott Wood
2012-02-17 0:23 ` Alexander Graf
2012-02-17 18:27 ` Scott Wood
2012-02-18 9:49 ` Avi Kivity [this message]
2012-02-17 0:19 ` Alexander Graf
2012-02-18 10:00 ` Avi Kivity
2012-02-18 10:43 ` Alexander Graf
2012-02-15 19:17 ` Scott Wood
2012-02-12 7:10 ` Takuya Yoshikawa
2012-02-15 13:32 ` Avi Kivity
2012-02-07 15:23 ` Anthony Liguori
2012-02-07 15:28 ` Alexander Graf
2012-02-08 17:20 ` Alan Cox
2012-02-15 13:33 ` Avi Kivity
2012-02-15 22:14 ` Arnd Bergmann
2012-02-10 3:07 ` Jamie Lokier
2012-02-03 18:07 ` Eric Northup
2012-02-03 22:52 ` [Qemu-devel] " Anthony Liguori
2012-02-06 19:46 ` Scott Wood
2012-02-07 6:58 ` Michael Ellerman
2012-02-07 10:04 ` Alexander Graf
2012-02-15 22:21 ` Arnd Bergmann
2012-02-16 1:04 ` Michael Ellerman
2012-02-16 19:28 ` Avi Kivity
2012-02-17 0:09 ` Michael Ellerman
2012-02-18 10:03 ` Avi Kivity
2012-02-16 10:26 ` Avi Kivity
2012-02-07 12:28 ` Anthony Liguori
2012-02-07 12:40 ` Avi Kivity
2012-02-07 12:51 ` Anthony Liguori
2012-02-07 13:18 ` Avi Kivity
2012-02-07 15:15 ` Anthony Liguori
2012-02-07 18:28 ` Chris Wright
2012-02-08 17:02 ` Scott Wood
2012-02-08 17:12 ` Alan Cox
2012-02-05 9:37 ` Gleb Natapov
2012-02-05 9:44 ` Avi Kivity
2012-02-05 9:51 ` Gleb Natapov
2012-02-05 9:56 ` Avi Kivity
2012-02-05 10:58 ` Gleb Natapov
2012-02-05 13:16 ` Avi Kivity
2012-02-05 16:36 ` [Qemu-devel] " Anthony Liguori
2012-02-06 9:34 ` Avi Kivity
2012-02-06 13:33 ` Anthony Liguori
2012-02-06 13:54 ` Avi Kivity
2012-02-06 14:00 ` Anthony Liguori
2012-02-06 14:08 ` Avi Kivity
2012-02-07 18:12 ` Rusty Russell
2012-02-15 13:39 ` Avi Kivity
2012-02-15 21:59 ` Anthony Liguori
2012-02-16 8:57 ` Gleb Natapov
2012-02-16 14:46 ` Anthony Liguori
2012-02-16 19:34 ` Avi Kivity
2012-02-15 23:08 ` Rusty Russell
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