Messages in this thread | | | Date | Fri, 16 Jan 2009 13:47:34 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] i386: fix assumed to be contiguous leaf page tables for kmap_atomic region (take 2) |
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* Jan Beulich <jbeulich@novell.com> wrote:
> Debugging and original patch from Nick Piggin <npiggin@suse.de> > > The early fixmap pmd entry inserted at the very top of the KVA is causing the > subsequent fixmap mapping code to not provide physically linear pte pages over > the kmap atomic portion of the fixmap (which relies on said property to > calculate pte addresses). > > This has caused weird boot failures in kmap_atomic much later in the boot > process (initial userspace faults) on a 32-bit PAE system with a larger number > of CPUs (smaller CPU counts tend not to run over into the next page so don't > show up the problem). > > Solve this by attempting to clear out the page table, and copy any of its > entries to the new one. Also, add a bug if a nonlinear condition is encountered > and can't be resolved, which might save some hours of debugging if this fragile > scheme ever breaks again... > > Signed-off-by: Nick Piggin <npiggin@suse.de> > > Once we have such logic, we can also use it to eliminate the early ioremap > trickery around the page table setup for the fixmap area. This also fixes > potential issues with FIX_* entries sharing the leaf page table with the early > ioremap ones getting discarded by early_ioremap_clear() and not restored by > early_ioremap_reset(). It at once eliminates the temporary (and configuration, > namely NR_CPUS, dependent) unavailability of early fixed mappings during the > time the fixmap area page tables get constructed. > > Finally, also replace the hard coded calculation of the initial table space > needed for the fixmap area with a proper one, allowing kernels configured for > large CPU counts to actually boot. > > Signed-off-by: Jan Beulich <jbeulich@novell.com> > > --- > arch/x86/include/asm/io.h | 1 > arch/x86/mm/init_32.c | 48 +++++++++++++++++++++++++++++++++++++++++++--- > arch/x86/mm/ioremap.c | 25 ----------------------- > 3 files changed, 45 insertions(+), 29 deletions(-)
Much cleaner - applied to tip/x86/urgent, thanks Jan!
Ingo
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