linux-kernel - Re: Why preallocate pmd in x86 32-bit PAE?

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:	Fri, 16 Nov 2007 11:14:36 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	William Lee Irwin III <wli@...omorphy.com>,
	Andi Kleen <ak@...e.de>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Why preallocate pmd in x86 32-bit PAE?

Linus Torvalds wrote:
> So don't do it. Just preallocate for the magic 4-entry PGD. You can make 
> the special case just be something like
>   

Yes, OK, it makes sense.  Conceptually they would be dynamically
allocated and freed, but they'd just happen to start allocated, to avoid
the tlb flush of populating the pgd of an active pagetable.  If you
happened to do a 1G munmap, it may end up freeing and reallocating them,
but that's going to be very rare.  Either way, the other special cases
are avoided (though pgd_populate would still need to be correct, on the
offchance it gets invoked).

    J
-
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/