Message-ID: <4417454F.2080908@vmware.com>
Date: Tue, 14 Mar 2006 14:35:59 -0800
From: Zachary Amsden <zach@vmware.com>
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To: Chris Wright <chrisw@sous-sol.org>
Cc: Linus Torvalds <torvalds@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Virtualization Mailing List <virtualization@lists.osdl.org>,
       Xen-devel <xen-devel@lists.xensource.com>,
       Andrew Morton <akpm@osdl.org>, Dan Hecht <dhecht@vmware.com>,
       Dan Arai <arai@vmware.com>, Anne Holler <anne@vmware.com>,
       Pratap Subrahmanyam <pratap@vmware.com>,
       Christopher Li <chrisl@vmware.com>, Joshua LeVasseur <jtl@ira.uka.de>,
       Rik Van Riel <riel@redhat.com>, Jyothy Reddy <jreddy@vmware.com>,
       Jack Lo <jlo@vmware.com>, Kip Macy <kmacy@fsmware.com>,
       Jan Beulich <jbeulich@novell.com>,
       Ky Srinivasan <ksrinivasan@novell.com>,
       Wim Coekaerts <wim.coekaerts@oracle.com>,
       Leendert van Doorn <leendert@watson.ibm.com>,
       Gerd Hoffmann <kraxel@suse.de>
Subject: Re: [RFC, PATCH 7/24] i386 Vmi memory hole
References: <200603131804.k2DI4N6s005678@zach-dev.vmware.com> <20060314064107.GK12807@sorel.sous-sol.org> <44166D6B.4090701@vmware.com> <20060314215616.GM12807@sorel.sous-sol.org>
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Chris Wright wrote:
> * Zachary Amsden (zach@vmware.com) wrote:
>   
>> Allow creation of an compile time hole at the top of linear address space.
>>
>> Extended to allow a dynamic hole in linear address space, 7/2005.  This
>> required some serious hacking to get everything perfect, but the end result
>> appears to function quite nicely.  Everyone can now share the appreciation
>> of pseudo-undocumented ELF OS fields, which means core dumps, debuggers
>> and even broken or obsolete linkers may continue to work.
>>     
>
> Thanks.  Gerd did something similar (although I believe it's simpler,
> don't recall the relocation magic) for Xen.  Either way, it's useful
> from Xen perspective.
>   

I believe Xen disables sysenter.  The complications in my patch come 
from the fact that the vsyscall page has to be relocated dynamically, 
requiring, basically run time linking on the page and some tweaks to get 
sysenter to work.  If you don't use vsyscall (say, non-TLS glibc), then 
you don't need that complexity.  But I think it might be needed now, 
even for Xen.

Zach
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