Hi, Nathan,
On Wed, Jun 28, 2023 at 5:28 AM Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
>
> Hi Huacai,
>
> + Masahiro
>
> On Tue, Jun 27, 2023 at 11:11:27AM +0800, Huacai Chen wrote:
> > Hi, Nathan,
> >
> > On Tue, Jun 27, 2023 at 12:07 AM Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
> > >
> > > On Mon, Jun 26, 2023 at 03:50:47PM +0800, Huacai Chen wrote:
> > > > After commit 0e96ea5c3eb5904e5dc2f ("MIPS: Loongson64: Clean up use of
> > > > cc-ifversion") we get a build error when make modules_install:
> > > >
> > > > cc1: error: '-mloongson-mmi' must be used with '-mhard-float'
> > > >
> > > > The reason is when make modules_install, 'call cc-option' doesn't work
> > > > in $(KBUILD_CFLAGS) of 'CHECKFLAGS'. Then there is no -mno-loongson-mmi
> > > > applied and -march=loongson3a enable MMI instructions.
> > >
> > > The first sentence does not make much sense to me, specifically "in
> > > $(KBUILD_CFLAGS) of 'CHECKFLAGS'". What configuration and build command
> > > reproduces this? I do not see how '-mno-loongson-mmi' would fail to get
> > > added to cflags-y after 0e96ea5c3eb5, which should have had no
> > > functional change... I don't want to hang this change up since there is
> > > real breakage but I want to make sure we fully understand why
> > > 0e96ea5c3eb5 broke things and why this patch resolves it.
> > Please use loongson3_defconfig to build a loongson kernel with
> > toolchains from here [1]:
> > 'make' will succeed, but there is a build error when 'make
> > modules_install'. And you should be careful because 'make
> > modules_install' doesn't stop when the error occurs.
>
> Excellent, thank you! I understand what is going on here and your patch
> should work to resolve it (although I think the commit message should be
> flushed out a little more with the following details) but I am curious
> if Masahiro has any thoughts around this.
>
> As you note, the error message comes from the CHECKFLAGS invocation of
> $(CC) but it has no impact on the final result of modules_install, it is
> purely a cosmetic issue from what I can tell. The error occurs because
> cc-option is defined in scripts/Makefile.compiler, which is not included
> in Makefile when running modules_install, as install targets are not
> supposed to require the compiler; see commit 805b2e1d427a ("kbuild:
> include Makefile.compiler only when compiler is needed"). As a result,
> the call to check for '-mno-loongson-mmi' just never happens.
>
> It would nice if '-mno-loongson-mmi' could be added unconditionally when
> using GCC but I can see that the flag has only existed since 9.x, so we
> do need to keep the cc-option call.
>
> I am fine with your change as long as it includes some of the above
> information (basically noting that while the original change should have
> been equivalent, the requirement of '-mno-loongson-mmi' when using
> certain Loongson '-march=' values with '-msoft-float' means that those
> Loongson '-march=' values need to be called with cc-option as well),
> even if clang will incur two more cc-option calls as a result (not the
> end of the world).
>
> Additionally, it seems like the same issue will occur when running
> modules_install when CONFIG_CPU_LOONGSON2E or CONFIG_CPU_LOONGSON2F are
> enabled, which I guess I also broke in commit 13ceb48bc19c ("MIPS:
> Loongson2ef: Remove unnecessary {as,cc}-option calls") :/
>
> Sorry again for the breakage and thanks for the fix!
OK, I will update the commit message and fix for LOONGSON2EF together.
Huacai
>
> Cheers,
> Nathan
>
> > > > Fix this by partially reverting to the old logic, use 'call cc-option'
> > > > to conditionally apply -march=loongson3a and -march=mips64r2.
> > > >
> > > > Fixes: 0e96ea5c3eb5904e5dc2f ("MIPS: Loongson64: Clean up use of cc-ifversion")
> > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
> > > > Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> > > > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > > > ---
> > > > arch/mips/Makefile | 5 +----
> > > > 1 file changed, 1 insertion(+), 4 deletions(-)
> > > >
> > > > diff --git a/arch/mips/Makefile b/arch/mips/Makefile
> > > > index a7a4ee66a9d3..7fb76d12829e 100644
> > > > --- a/arch/mips/Makefile
> > > > +++ b/arch/mips/Makefile
> > > > @@ -186,11 +186,8 @@ cflags-$(CONFIG_CPU_LOONGSON2F) += -march=loongson2f -Wa,--trap
> > > > # Some -march= flags enable MMI instructions, and GCC complains about that
> > > > # support being enabled alongside -msoft-float. Thus explicitly disable MMI.
> > > > cflags-$(CONFIG_CPU_LOONGSON2EF) += $(call cc-option,-mno-loongson-mmi)
> > > > -ifdef CONFIG_CPU_LOONGSON64
> > > > cflags-$(CONFIG_CPU_LOONGSON64) += -Wa,--trap
> > > > -cflags-$(CONFIG_CC_IS_GCC) += -march=loongson3a
> > > > -cflags-$(CONFIG_CC_IS_CLANG) += -march=mips64r2
> > > > -endif
> > > > +cflags-$(CONFIG_CPU_LOONGSON64) += $(call cc-option,-march=loongson3a,-march=mips64r2)
> > > > cflags-$(CONFIG_CPU_LOONGSON64) += $(call cc-option,-mno-loongson-mmi)
> > > >
> > > > cflags-$(CONFIG_CPU_R4000_WORKAROUNDS) += $(call cc-option,-mfix-r4000,)
> > > > --
> > > > 2.39.3
> > > >
