Messages in this thread | | | Date | Sun, 13 Nov 2005 02:42:41 -0500 | From | Dave Jones <> | Subject | Re: [PATCH 1/10] Cr4 is valid on some 486s |
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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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