Messages in this thread | | | Date | Fri, 21 Mar 2008 19:44:30 +0100 | From | Andi Kleen <> | Subject | Re: [PATCH] [4/7] Don't use large pages to map the first 2/4MB of memory |
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On Fri, Mar 21, 2008 at 07:03:19PM +0100, Thomas Gleixner wrote: > On Fri, 21 Mar 2008, Andi Kleen wrote: > > > Also we split the first GB mapping anyway due to the various regions > > > (NX, RO, UC) in there. > > > > I didn't think so unless you have DEBUG_RODATA enabled? > > NX is independent of DEBUG_RODATA
Sure, but it is still not split by default. At least I don't see any code for that anywhere except in my own patchkit.
> and the RODATA protection should be > made unconditional on anyway.
Requiring hundreds instead of two TLB entries for the kernel text?
I must say I personally cannot ever remember any bug caught by RODATA anyways, so I am a bit dubious on its value.
> > Also there > > should be no UC region there as known by the kernel. There might > > be a WC region there from the frame buffer code, but that is an MTRR, > > not a pageattr. > > The first ioremap of the PCI space splits the GB page as well.
PCI space is normally in the fourth or sometimes third GB page, not in the first. I am not aware of any system that has the PCI hole in the first GB.
-Andi
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