Messages in this thread | | | From | Michael Ellerman <> | Subject | RE: [PATCH] powerpc/32: Move entry_32 functions just after HEAD functions. | Date | Thu, 20 Apr 2017 21:25:32 +1000 |
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David Laight <David.Laight@ACULAB.COM> writes:
> From: Christophe Leroy >> By default, PPC8xx PINs an ITLB on the first 8M of memory in order >> to avoid any ITLB miss on kernel code. >> However, with some debug functions like DEBUG_PAGEALLOC and >> (soon to come) DEBUG_RODATA, the PINned TLB is invalidated soon >> after startup so ITLB missed start to happen also on the kernel code. >> >> In order to avoid any ITLB miss in a critical section, we have to >> ensure that their is no page boundary crossed between the setup of >> a new value in SRR0/SRR1 and the associated RFI. This cannot be done >> easily if entry_32 functions sits in the middle of other .text >> functions. By placing entry_32 just after the .head section (as already >> done for entry_64 on PPC64), we can more easily ensure the issue >> doesn't happen. > > Shouldn't this be done by putting all the functions that 'matter' > into a named section instead of relying on the order of the input files? > (Which is what I think this is doing.)
Yeah that is fragile if there's nothing more to it.
I'm not sure if we need a special section. If the functions that must not cross a page boundary are aligned to a page boundary (with .align) then that would also work wouldn't it?
cheers
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