linux-kernel - Re: [PATCH 2/3] powerpc: fix build errors

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Message-ID: <CADYN=9L7L7+DOA6qYj4aOgg9rBhOrUCk5b4K5tr6wZ709WpsyA@mail.gmail.com>
Date:   Thu, 24 Feb 2022 17:12:09 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 2/3] powerpc: fix build errors

On Thu, 24 Feb 2022 at 13:39, Michael Ellerman <mpe@...erman.id.au> wrote:
>
> Hi Anders,

Hi Michael,

>
> Thanks for these, just a few comments below ...

I will resolve the comments below and resend a v2 shortly.

Cheers,
Anders

>
> Anders Roxell <anders.roxell@...aro.org> writes:
> > Building tinyconfig with gcc (Debian 11.2.0-16) and assembler (Debian
> > 2.37.90.20220207) the following build error shows up:
> >
> >  {standard input}: Assembler messages:
> >  {standard input}:1190: Error: unrecognized opcode: `stbcix'
> >  {standard input}:1433: Error: unrecognized opcode: `lwzcix'
> >  {standard input}:1453: Error: unrecognized opcode: `stbcix'
> >  {standard input}:1460: Error: unrecognized opcode: `stwcix'
> >  {standard input}:1596: Error: unrecognized opcode: `stbcix'
> >  ...
> >
> > Rework to add assembler directives [1] around the instruction. Going
> > through the them one by one shows that the changes should be safe.  Like
> > __get_user_atomic_128_aligned() is only called in p9_hmi_special_emu(),
> > which according to the name is specific to power9.  And __raw_rm_read*()
> > are only called in things that are powernv or book3s_hv specific.
> >
> > [1] https://sourceware.org/binutils/docs/as/PowerPC_002dPseudo.html#PowerPC_002dPseudo
> >
> > Cc: <stable@...r.kernel.org>
> > Co-developed-by: Arnd Bergmann <arnd@...db.de>
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
> > ---
> >  arch/powerpc/include/asm/io.h        | 46 +++++++++++++++++++++++-----
> >  arch/powerpc/include/asm/uaccess.h   |  3 ++
> >  arch/powerpc/platforms/powernv/rng.c |  6 +++-
> >  3 files changed, 46 insertions(+), 9 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
> > index beba4979bff9..5ff6dec489f8 100644
> > --- a/arch/powerpc/include/asm/io.h
> > +++ b/arch/powerpc/include/asm/io.h
> > @@ -359,25 +359,37 @@ static inline void __raw_writeq_be(unsigned long v, volatile void __iomem *addr)
> >   */
> >  static inline void __raw_rm_writeb(u8 val, volatile void __iomem *paddr)
> >  {
> > -     __asm__ __volatile__("stbcix %0,0,%1"
> > +     __asm__ __volatile__(".machine \"push\"\n"
> > +                          ".machine \"power6\"\n"
> > +                          "stbcix %0,0,%1\n"
> > +                          ".machine \"pop\"\n"
> >               : : "r" (val), "r" (paddr) : "memory");
>
> As Segher said it'd be cleaner without the embedded quotes.
>
> > @@ -441,7 +465,10 @@ static inline unsigned int name(unsigned int port)       \
> >       unsigned int x;                                 \
> >       __asm__ __volatile__(                           \
> >               "sync\n"                                \
> > +             ".machine \"push\"\n"                   \
> > +             ".machine \"power6\"\n"                 \
> >               "0:"    op "    %0,0,%1\n"              \
> > +             ".machine \"pop\"\n"                    \
> >               "1:     twi     0,%0,0\n"               \
> >               "2:     isync\n"                        \
> >               "3:     nop\n"                          \
> > @@ -465,7 +492,10 @@ static inline void name(unsigned int val, unsigned int port) \
> >  {                                                    \
> >       __asm__ __volatile__(                           \
> >               "sync\n"                                \
> > +             ".machine \"push\"\n"                   \
> > +             ".machine \"power6\"\n"                 \
> >               "0:" op " %0,0,%1\n"                    \
> > +             ".machine \"pop\"\n"                    \
> >               "1:     sync\n"                         \
> >               "2:\n"                                  \
> >               EX_TABLE(0b, 2b)                        \
>
> It's not visible from the diff, but the above two are __do_in_asm and
> __do_out_asm and are inside an ifdef CONFIG_PPC32.
>
> AFAICS they're only used for:
>
> __do_in_asm(_rec_inb, "lbzx")
> __do_in_asm(_rec_inw, "lhbrx")
> __do_in_asm(_rec_inl, "lwbrx")
> __do_out_asm(_rec_outb, "stbx")
> __do_out_asm(_rec_outw, "sthbrx")
> __do_out_asm(_rec_outl, "stwbrx")
>
> Which are all old instructions, so I don't think we need the machine
> power6 for those two macros?
>
> > diff --git a/arch/powerpc/platforms/powernv/rng.c b/arch/powerpc/platforms/powernv/rng.c
> > index b4386714494a..5bf30ef6d928 100644
> > --- a/arch/powerpc/platforms/powernv/rng.c
> > +++ b/arch/powerpc/platforms/powernv/rng.c
> > @@ -43,7 +43,11 @@ static unsigned long rng_whiten(struct powernv_rng *rng, unsigned long val)
> >       unsigned long parity;
> >
> >       /* Calculate the parity of the value */
> > -     asm ("popcntd %0,%1" : "=r" (parity) : "r" (val));
> > +     asm (".machine \"push\"\n"
> > +          ".machine \"power7\"\n"
> > +          "popcntd %0,%1\n"
> > +          ".machine \"pop\"\n"
> > +          : "=r" (parity) : "r" (val));
>
> This was actually present in an older CPU, but it doesn't really matter,
> this is fine.
>
> cheers