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From: Toshi Kani <toshi.kani@hpe.com>
To: "Luis R. Rodriguez" <mcgrof@suse.com>
Cc: Prarit Bhargava <prarit@redhat.com>,
	Stuart Hayes <stuart.w.hayes@gmail.com>,
	tglx@linutronix.de, mingo@redhat.com,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	mcgrof@do-not-panic.com, Toshi Kani <toshi.kani@hp.com>,
	Jan Beulich <JBeulich@suse.com>, Juergen Gross <jgross@suse.com>
Subject: Re: Fwd: [PATCH] x86: Use larger chunks in mtrr_cleanup
Date: Thu, 03 Sep 2015 18:48:46 -0600	[thread overview]
Message-ID: <1441327726.3277.109.camel@hpe.com> (raw)
In-Reply-To: <20150903235429.GZ8051@wotan.suse.de>

On Fri, 2015-09-04 at 01:54 +0200, Luis R. Rodriguez wrote:
> On Thu, Sep 03, 2015 at 05:21:14PM -0600, Toshi Kani wrote:
> > On Fri, 2015-09-04 at 00:45 +0200, Luis R. Rodriguez wrote:
> > > On Thu, Sep 03, 2015 at 04:25:31PM -0600, Toshi Kani wrote:
 :
> > > > On Xen,
> > > 
> > > When Xen is used a platform firmware may still set up MTRR, even if the
> > > hypervisor doesn't set up MTRR right ? So same issue and question here.
> > 
> > Right, I meant to say Xen guests.
> 
> Ah but its import complicated than that.
> 
> > In case of the Xen hypervisor,
> > mtrr_type_lookup() returns a valid type as it runs on a platform.
> 
> I am not sure if this happens today, I know MTRR is simply disabled by
> the Xen Hypervisor on the CPU explicitly, it disable it so guests reading
> the MTRR capabilities sees it as disabled when queried.

Oh, I would not let the hypervisor to disable MTRRs...

> Then since the Xen Linux guests cannot speak MTRR through the hypervisor
> (for instance Xen guests cannot ask Xen hypervisor to mtrr_type_lookup() for
> it) if PCI passthrough is used it could mean a guest might set up / use
> incorrect info as well.
> 
> If I undestand this correctly then I think we're in a pickle with Xen unless
> we add hypervisor support and hypercall support for mtrr_type_lookup().

I was under assumption that MTRRs are emulated and disabled on guests.  Isn't
guest physical address virtualized?  I know other proprietary VMMs on IA64,
but know nothing about Xen...  So, please disregard my comments to Xen. :-)

Thanks,
-Toshi

  reply	other threads:[~2015-09-04  0:51 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <55E477DE.2060106@gmail.com>
2015-08-31 16:05 ` Stuart Hayes
2015-09-03  2:45   ` Luis R. Rodriguez
2015-09-03 12:17     ` Prarit Bhargava
2015-09-03 17:59       ` Luis R. Rodriguez
2015-09-03 18:10         ` Prarit Bhargava
2015-09-03 18:40           ` Luis R. Rodriguez
2015-09-03 19:22             ` Toshi Kani
2015-09-03 19:51               ` Luis R. Rodriguez
2015-09-03 21:31                 ` Toshi Kani
2015-09-03 22:07                   ` Luis R. Rodriguez
2015-09-03 22:25                     ` Toshi Kani
2015-09-03 22:45                       ` Luis R. Rodriguez
2015-09-03 23:21                         ` Toshi Kani
2015-09-03 23:54                           ` Luis R. Rodriguez
2015-09-04  0:48                             ` Toshi Kani [this message]
2015-09-04  1:40                               ` Luis R. Rodriguez
2015-09-04 14:56                                 ` Toshi Kani
2015-09-04  6:51                             ` Jan Beulich
2015-09-14 14:46       ` Stuart Hayes
2015-11-05 19:14         ` Yinghai Lu
2015-11-05 19:43           ` Luis R. Rodriguez
2016-03-16 20:20             ` Luis R. Rodriguez
2016-03-29 17:07               ` Luis R. Rodriguez

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