Messages in this thread | | | Date | Thu, 16 Jul 2015 19:19:29 +0100 | From | Will Deacon <> | Subject | Re: [PATCH] arm64: alternative: Provide if/else/endif assembler macros |
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Hi Daniel,
On Fri, Jul 10, 2015 at 02:48:50PM +0100, Daniel Thompson wrote: > The existing alternative_insn macro has some limitations that make it > hard to work with. In partiuclar the fact it takes instructions from it > own macro arguments means it doesn't play very nicely with C pre-processor > macros because the macro arguments look like a string to the C > pre-processor. Workarounds are (probably) possible but things start to > look ugly. > > Introduce an alternative set of macros that allows instructions to be > presented to the assembler as normal and switch everything over to the > new macros. > > Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> > --- > > Notes: > To be honest these if not/else/endif macros are simply more readable > than the original macro and that might be enough to justify them on > their own. However below is an example that is needlessly hard to > write without them because ICC_PMR_EL1 is a C pre-processor macro. > > .macro disable_irq, tmp > mov \tmp, #ICC_PMR_EL1_MASKED > alternative_if_not ARM64_HAS_SYSREG_GIC_CPUIF > msr daifset, #2 > alternative_else > msr_s ICC_PMR_EL1, \tmp > alternative_endif > .endm > > The new macros have received a fair degree of testing because I have > based my (not published since March) pseudo-NMI patch set on them. > > arch/arm64/include/asm/alternative.h | 18 ++++++++++++------ > arch/arm64/kernel/entry.S | 29 +++++++++++++---------------- > arch/arm64/kvm/hyp.S | 12 ++++++++++-- > arch/arm64/mm/cache.S | 7 ++++++- > 4 files changed, 41 insertions(+), 25 deletions(-)
After some consideration, I think I prefer your suggestion over what we currently have in mainline. However, there are a bunch of patches that are candidates for 4.3 which will conflict horribly with this.
Would you be able to:
(1) Split this up so that you have a patch introducing the new macro, then a patch converting entry.S and cache.S then a separate one for kvm/hyp.S?
(2) Keep alternative_insn around for the moment
(3) Once the dust has settled for 4.3, we can see how easy the old macro is to remove
Sound ok to you?
Cheers,
Will
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