linux-kernel - Re: PAE and PSE ??

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

Date:	Sun, 22 Oct 2006 16:37:27 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Sandeep Kumar <sandeepksinha@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: PAE and PSE ??

Rafael J. Wysocki wrote:
> Hi,
> 
> On Sunday, 22 October 2006 08:29, Sandeep Kumar wrote:
>> Hi all,
>> I have read in UTLK by bovet that the linux kernel does not uses the
>> PSE bit on an x86
>> machine. Then how come we have the hugetlbfs, which provides support
>> for 4MB pages ?
> 
> AFAIK, PSE is only used when PAE is not set and then it enables the 4 MB
> pages.  If PAE is set, the 4 MB pages are impossible because there are only
> 512 entries per page table, but 2 MB pages can be used instead (and you don't
> need to set PSE to use them).
> 

You're wrong.

PSE refers to 4 MB pages when PAE is not used, and 2 MB pages when PAE 
is used.

In theory, you could have PAE without PSE, which would only support 4K 
pages.

Linux uses PSE; it may or may not use PAE depending on the configuration.

	-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/