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From: "Jan Beulich" <JBeulich@suse.com>
To: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>
Cc: <stefan.bader@canonical.com>, <david.vrabel@citrix.com>,
	"xen-devel" <xen-devel@lists.xenproject.org>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	<chuck.anderson@oracle.com>, "Juergen Gross" <JGross@suse.com>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [Xen-devel] XSA 154 and ISA region (640K -> 1MB) WB cache instead of UC
Date: Thu, 18 Aug 2016 05:12:54 -0600	[thread overview]
Message-ID: <57B5B4560200007800107092@prv-mh.provo.novell.com> (raw)
In-Reply-To: <47fabc70-4500-1035-7dc7-7f0a3915471f@citrix.com>

>>> On 18.08.16 at 12:16, <andrew.cooper3@citrix.com> wrote:
> On 18/08/16 11:06, Jan Beulich wrote:
>>>>> On 17.08.16 at 22:32, <konrad.wilk@oracle.com> wrote:
>>>    Looking at the kernel it assumes that WB is ok for 640KB->1MB.
>>>    The comment says:
>>>    " /* Low ISA region is always mapped WB in page table. No need to track 
> *"
>> As per above it's not clear to me what this comment is backed by.
> 
> This states what is in the pagetables.  Not the combined result with MTRRs.
> 
> WB in the pagetables and WC/UB in the MTRRs is a legal combination which
> functions correctly.

True, but then again - haven't I been told multiple times that Linux
nowadays prefers to run without using MTRRs?

Jan

  reply	other threads:[~2016-08-18 11:12 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-17 20:32 XSA 154 and ISA region (640K -> 1MB) WB cache instead of UC Konrad Rzeszutek Wilk
2016-08-17 20:32 ` Konrad Rzeszutek Wilk
2016-08-18 10:06 ` Jan Beulich
2016-08-18 10:06 ` Jan Beulich
2016-08-18 10:16   ` Andrew Cooper
2016-08-18 10:16   ` [Xen-devel] " Andrew Cooper
2016-08-18 11:12     ` Jan Beulich [this message]
2016-08-18 15:35       ` One Thousand Gnomes
2016-08-18 15:35         ` One Thousand Gnomes
2016-08-19 15:27         ` [Xen-devel] " Konrad Rzeszutek Wilk
2016-08-19 15:27           ` Konrad Rzeszutek Wilk
2016-08-18 11:12     ` Jan Beulich
2016-08-19 14:52   ` Konrad Rzeszutek Wilk
2016-08-19 14:52     ` Konrad Rzeszutek Wilk
2016-08-19 15:14     ` Jan Beulich
2016-08-19 15:14       ` Jan Beulich

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