Messages in this thread | | | Date | Thu, 07 Aug 2008 23:10:25 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH]Fix broken VMI in 2.6.27-rc.. |
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H. Peter Anvin wrote: > Jeremy Fitzhardinge wrote: >>> >>> The Linux kernel was never a paragon of perfection - it was never >>> meant to be. Just because a bit of cruft went unnoticed into the >>> kernel doesn't mean we shouldn't fix it. >> >> I don't really see what the issue is. >> >> Fixmaps are primarily used for things that need to be mapped early >> before we can allocate address space dynamically. They're >> predominantly used for boot-time init, and rarely on any >> performance-critical path. The only vaguely regular use a fixmap >> gets during runtime is poking at apics, and that's dominated by IO >> time, and kmap_atomic. Statically, there's only 100 references in >> the kernel. And it only affects 32-bit. >> >> Having fixmaps at link-time fixed addresses would be nice, I suppose, >> but hardly worth going to vast effort over. >> > > No, but it's hardly vast effort, either.
Thinking about it, the fixmap really has to be as high as possible. If it were any lower, then it would either truncate the 1:1 mapping, or shadow some physical memory.
J
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