On Wed, 2018-02-07 at 13:17 +0100, Martin Schwidefsky wrote: > On Wed, 07 Feb 2018 12:07:55 +0000 > David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > > > > > On Wed, 2018-02-07 at 11:07 +0100, Pavel Machek wrote: > > > > > > This is really unfortunate naming of kernel option. > > > > > > spectre_v2=off sounds like we are turning the "bug" off, but i somehow > > > suspect you are turning the bug _workaround_ off. > > That's consistent with what we have on x86. > > > > > > > > > > > > > +ifdef CONFIG_EXPOLINE > > > > + ifeq ($(call cc-option-yn,$(CC_FLAGS_MARCH) -mindirect-branch=thunk),y) > > > > + CC_FLAGS_EXPOLINE := -mindirect-branch=thunk > > > > + CC_FLAGS_EXPOLINE += -mfunction-return=thunk > > > > + CC_FLAGS_EXPOLINE += -mindirect-branch-table > > > > + export CC_FLAGS_EXPOLINE > > > > + cflags-y += $(CC_FLAGS_EXPOLINE) > > > > + else > > > > + $(warning "Your gcc lacks the -mindirect-branch= option") > > > > + endif > > > > +endif > > That isn't, though. Linus asked us to drop the $(warning) part. > > > > ... and then spent a week building with a non-retpoline compiler and > > not noticing, so he might have changed his mind ;) > > I found the warning to have some value, it helps for the case where my > fingers are faster than my brain and I type "make" instead of "smake" > which uses the alternative compiler with the required support. > > @Linus: do you want a warning or prefer not to have one ? FWIW I agreed to drop it when the plan in my head was "we'll just turn on IBRS instead if the compiler doesn't do full retpoline support". Now that Linus has expressed a disinclination to take IBRS support in that form, I might be more inclined to defend the $(warning) too.
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