Re: [uml-devel] Recent patches of note

[Bodo Stroesser <bstroesser@fujitsu-siemens.com>]

Jeff Dike wrote:
> On Thu, Jun 16, 2005 at 08:51:20PM +0200, Blaisorblade wrote:
> 
>>>And also it makes tt a bit more removable, if Jeff decides to.
>>
>>Well, on this point I'd be cautious.
>>
>>Currently there is no way to even test UML in SMP mode other than using TT 
>>mode, so at least this must be solved.
> 
> 
> Yeah, we need to provide SMP on skas.  That, and the performance of page fault
> handling were the only two things stopping me from removing tt mode in favor
> of skas0.
> 
> Bodo and have talked about this, and it seems that skas0 SMP is impractical
> because a malicious threaded app could interfere with the stub operation.
> 
> However, skas3 SMP is quite doable, and I think an unsafe skas0 SMP mode
> that you can enable with a switch might be OK, too.
> 
> I've since decided that page fault performance is not a show-stopper.  It
> appears that tt mode is not supportable in recent libcs due to the errno
> problem. 
> 
> We can get page fault performance back by pushing PTRACE_FAULTINFO into 
> mainline, which should have been done a long time ago.  Same for sysemu, 
> BTW.
> 
> At this point, I'm -><- this close to deciding to get rid of tt mode in
> 2.6.13 or 2.6.14.  I want skas0 in mainline early in 2.6.13 so it can
> be exercised.  Getting skas SMP fixed, and PTRACE_FAULTINFO in mainline
> would make me happy about trashing tt mode at some later point.
> 
> 				Jeff
To make skas3 consistent, we should have a mainline version of add-stub-vmas.
Also, the LDT-changes should go in at the same time.

	Bodo


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