On Sun, Aug 22, 2021 at 1:31 AM Ingo Molnar <mingo@xxxxxxxxxx> wrote: > > > * tip-bot2 for Nick Desaulniers <tip-bot2@xxxxxxxxxxxxx> wrote: > > > The following commit has been merged into the x86/build branch of tip: > > > > Commit-ID: 1463c2a27d59c69358ad1cbd869d3a8649695d8c > > Gitweb: https://git.kernel.org/tip/1463c2a27d59c69358ad1cbd869d3a8649695d8c > > Author: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > > AuthorDate: Thu, 12 Aug 2021 11:38:48 -07:00 > > Committer: Borislav Petkov <bp@xxxxxxx> > > CommitterDate: Sun, 15 Aug 2021 10:32:52 +02:00 > > > > x86/build: Remove stale cc-option checks > > > > -mpreferred-stack-boundary= is specific to GCC, while -mstack-alignment= > > is specific to Clang. Rather than test for this three times via > > cc-option and __cc-option, rely on CONFIG_CC_IS_* from Kconfig. > > > > GCC did not support values less than 4 for -mpreferred-stack-boundary= > > until GCC 7+. Change the cc-option test to check for a value of 2, > > rather than 4. > > > --- a/arch/x86/Makefile > > +++ b/arch/x86/Makefile > > @@ -14,10 +14,13 @@ endif > > > > # For gcc stack alignment is specified with -mpreferred-stack-boundary, > > # clang has the option -mstack-alignment for that purpose. > > -ifneq ($(call cc-option, -mpreferred-stack-boundary=4),) > > +ifdef CONFIG_CC_IS_GCC > > +ifneq ($(call cc-option, -mpreferred-stack-boundary=2),) > > cc_stack_align4 := -mpreferred-stack-boundary=2 > > cc_stack_align8 := -mpreferred-stack-boundary=3 > > -else ifneq ($(call cc-option, -mstack-alignment=16),) > > +endif > > +endif > > +ifdef CONFIG_CC_IS_CLANG > > cc_stack_align4 := -mstack-alignment=4 > > cc_stack_align8 := -mstack-alignment=8 > > So I spent most of yesterday bisecting a hard to diagnose bug that looked > like a GPU driver bug - but the bisect somewhat surprisingly ended up at > this commit. I'm genuinely sorry about that. Let me guess, GPF on SSE instruction with stack based operand from AMDGPU? (I've seen that twice so far related to these options.) I see now what went wrong.... GCC only supports a 4B stack alignment for ***32b*** (or 16b) x86; `-mpreferred-stack-boundary=2` will produce an error unless -m32 or -m16 is set; but `-mpreferred-stack-boundary=2 -m32` has been long supported. It's -mpreferred-stack-boundary=3 for -m64 that wasn't supported until the gcc-7 release. So the cc-option test should instead test -mpreferred-stack-boundary=3. > > Doing the partial revert below solves the regression - as the above hunk is > not obviously an identity transformation. I have a pretty usual GCC 10.3.0 > build environment with nothing exotic. > > I amdended the commit with the partial revert in tip:x86/build. No worries. I'll send a follow up. -- Thanks, ~Nick Desaulniers
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