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    DateSun, 13 Nov 2005 02:42:41 -0500
    FromDave Jones <>
    SubjectRe: [PATCH 1/10] Cr4 is valid on some 486s
    On Fri, Nov 11, 2005 at 12:22:07PM -0800, Linus Torvalds wrote:
     > 
     > 
     > On Fri, 11 Nov 2005, Zachary Amsden wrote:
     > > 
     > > Yes, this is fine, but is it worth writing the feature discovery code?  I
     > > suppose it doesn't matter, as it gets jettisoned after init.  I guess it is
     > > just preference.
     > 
     > Well, you could do the feature discovery by trying to take a fault early 
     > at boot-time. That's how we verify that write-protect works, and how we 
     > check that math exceptions come in the right way..
     > 
     > > Could we consider doing the same with LOCK prefix for SMP kernels booted on
     > > UP?  Evil grin.
     > 
     > Not so evil - I think it's been discussed. Not with alternates (not worth 
     > it), but it wouldn't be hard to do: just add a new section for "lock 
     > address", and have each inline asm that does a lock prefix do basically
     > 
     > 	1:
     > 		lock ; xyzzy
     > 
     > 	.section .lock.address
     > 	.long 1b
     > 	.previous
     > 
     > and then just walk the ".lock.address" thing and turn all locks into 0x90 
     > (nop).
    
    Looks like the Ubuntu people already did this...
    
    http://www.kernel.org/git/?p=linux/kernel/git/bcollins/ubuntu-2.6.git;a=commitdiff;h=048985336e32efe665cddd348e92e4a4a5351415;hp=1cb630c2b5aaad7cedaa78aa135e6cecf5ab91ac
    
    		Dave
    
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