linux-kernel - Re: Support for i386 PATs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Sat, 27 Jan 2007 23:54:08 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mikael Pettersson <mikpe@...uu.se>
CC:	linux-kernel@...r.kernel.org, thomas@...gstengraphics.com
Subject: Re: Support for i386 PATs

Mikael Pettersson wrote:
> 
> 3) Many Intel processors, including at least most P6s and probably
> also some P4s, have an erratum which effectively halves the number
> of available PAT entries, forcing an OS to make the low 4 and upper
> 4 PAT entries identical.
> 
> I don't know if 4 PAT types suffice for the kinds of uses people
> have in mind. But support for PAT would either have to restrict
> itself to only 4 PAT types, or ensure that it is only enabled on
> new enough processors where it actually works.
> 
> You will need to read all available Intel errata sheets (spec updates)
> to determine which processors are affected and which are OK.
> 

There aren't really that many useful caching types, so it probably 
doesn't matter all that much.

The types that matters most are WB, WC, and UC.  The fourth one could be 
WT, or it could be UC- (however, UC- can *always* be emulated by simply 
having the kernel being aware of the MTRR settings.)

	-hpa

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/