linux-kernel - Re: [PATCH] x86: set PAE PHYSICAL_MASK

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]

Message-ID: <48481846.6060407@kernel.org>
Date:	Thu, 05 Jun 2008 09:45:58 -0700
From:	"H. Peter Anvin" <hpa@...nel.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Jan Beulich <jbeulich@...ell.com>, Ingo Molnar <mingo@...e.hu>,
	Stable Kernel <stable@...nel.org>, x86@...nel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: set PAE PHYSICAL_MASK_SHIFT to match 64-bit

Jeremy Fitzhardinge wrote:
> 
> We could have an auction:
> 
>    Do I hear 46? 47? 48?  50?  52!  Going once, twice, 52 bits!
> 
> Anyway, we can fix it later in a separate patch.  This is a 
> change-as-little-as-possible bugfix patch.
> 

It should either be 52 bits or dynamic based on CPUID information.  The 
latter is very expensive.

If there end up being additional control bits assigned in this space we 
won't use them  since we know the size of the address space (which won't 
include the control bits) and thus will leave them at zero.

It's largely theoretical, since I believe Linux on x86-64 relies on 
virtual >= physical+N, where I believe N is about 3 bits, and the page 
table format or page size need to change to support more than 48 bits of 
virtual address space.

	-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/