From: "Jan Beulich" <jbeulich@suse.com>
To: <gnomes@lxorguk.ukuu.org.uk>
Cc: <stefan.bader@canonical.com>, <toshi.kani@hp.com>,
<x86@kernel.org>, <ville.syrjala@linux.intel.com>,
<xen-devel@lists.xensource.com>,
"Juergen Gross" <JGross@suse.com>, <linux-kernel@vger.kernel.org>,
<hpa@zytor.com>
Subject: Re: [Xen-devel] [PATCH RFC 0/3] x86: Full support of PAT
Date: Wed, 20 Aug 2014 13:21:22 +0100 [thread overview]
Message-ID: <53F4A0D202000078000BAD84@mail.emea.novell.com> (raw)
In-Reply-To: <20140820130511.771aeafa@alan.etchedpixels.co.uk>
>>> One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> 08/20/14 2:08 PM >>>
>> The Linux kernel currently supports only 4 different cache modes. The PAT MSR
>> is set up in a way that the setting of _PAGE_PAT in a pte doesn't matter: the
>> top 4 entries in the PAT MSR are the same as the 4 lower entries.
>>
>> This results in the kernel not supporting e.g. write-through mode. Especially
>> this cache mode would speed up drivers of video cards which now have to use
>> uncached accesses.
>
>Pentium II erratum A52 (and similar on quite a few other processors)
But you're aware that for the last two major releases Xen hasn't been supporting
32-bit CPUs at all anymore? I.e. why should we limit functionality under Xen
based on errata on 64-bit-incapable CPUs?
Jan
next prev parent reply other threads:[~2014-08-20 12:21 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-19 13:25 jgross
2014-08-19 13:25 ` [PATCH RFC 1/3] x86: Make page cache mode a real type jgross
2014-08-20 19:26 ` Toshi Kani
2014-08-21 9:30 ` [Xen-devel] " Juergen Gross
2014-08-22 9:24 ` Jan Beulich
2014-08-22 17:43 ` Toshi Kani
2014-08-21 22:09 ` Toshi Kani
2014-08-22 5:25 ` Juergen Gross
2014-08-19 13:25 ` [PATCH RFC 2/3] x86: Enable PAT to use cache mode translation tables jgross
2014-08-22 9:32 ` [Xen-devel] " Jan Beulich
2014-08-25 12:22 ` Juergen Gross
2014-08-19 13:25 ` [PATCH RFC 3/3] Support Xen pv-domains using PAT jgross
2014-08-20 12:05 ` [PATCH RFC 0/3] x86: Full support of PAT One Thousand Gnomes
2014-08-20 12:21 ` Jan Beulich [this message]
2014-08-20 22:00 ` [Xen-devel] " H. Peter Anvin
2014-08-20 12:35 ` Juergen Gross
2014-08-20 21:59 ` H. Peter Anvin
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