Messages in this thread | | | Date | Tue, 30 Jan 2018 14:10:20 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86: Fix overlap of i386 CPU_ENTRY_AREA with FIX_BTMAP |
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On Tue, 30 Jan 2018, William Grant wrote:
> Since commit 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the > fixmap"), i386's CPU_ENTRY_AREA has been mapped to the memory area just > below FIXADDR_START. But already immediately before FIXADDR_START is the > FIX_BTMAP area, which means that early_ioremap can collide with the > entry area. > > It's especially bad on PAE where FIX_BTMAP_BEGIN gets aligned to exactly > match CPU_ENTRY_AREA_BASE, so the first early_ioremap slot clobbers the > IDT and causes interrupts during early boot to reset the system. > > The overlap wasn't a problem before the CPU entry area was introduced, > as the fixmap has classically been preceded by the pkmap or vmalloc > areas, neither of which is used until early_ioremap is out of the > picture. > > Relocate CPU_ENTRY_AREA to below FIX_BTMAP, not just below the permanent > fixmap area.
Nice catch. I'm sure I stared at that more than once....
Thanks,
tglx
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