Messages in this thread | | | Date | Tue, 27 Oct 1998 21:09:47 +0100 (CET) | From | MOLNAR Ingo <> | Subject | Re: [patch] jiffies wraparound [Re: 2.1.125 Show stopper list: Draft] |
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On Tue, 27 Oct 1998, Linus Torvalds wrote:
> > But it would be a neat feature nevertheless, unfortunately exporting 4MB > > pages to ring 3 user-space doesnt seem to work (i've tried), only ring 0 > > is supposed to see those mappings. > > The VM layer currently gets confused if it sees a 4MB page. > > I actually had 4MB pages working at one point (with magic hackery to the > pmd_xxx macros - no generic VM changes necessary), but it became fairly > ugly, and the generated code was nasty for the normal case of 4kB pages.
my hack did it independently of the VM layer: fixing up the page table directly when /dev/mem gets mapped in a magic way. (this is unsafe but i just wanted to have a prototype first) I have tried really hard and others have told me it's the right conclusion, but i'll try it again. It would be a neat feature for XFree86 because it still happens quite often that the X server touches the framebuffer: line endings are sometimes nonstandard and have to be fixed up after an accel-line and small lines are faster in the framebuffer than setting up a whole accelerated operation. Plus font rendering is often done in the framebuffer too.
-- mingo
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