On Thu, 24 Feb 2022 at 13:39, Michael Ellerman <mpe@xxxxxxxxxxxxxx> 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@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> > Co-developed-by: Arnd Bergmann <arnd@xxxxxxxx>
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> > Signed-off-by: Anders Roxell <anders.roxell@xxxxxxxxxx>
> > ---
> > 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
