linux-kernel - Re: [PATCH] mips: DEC: honor CONFIG_MIPS_FP

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Date:   Fri, 4 Mar 2022 09:07:48 +0000 (GMT)
From:   "Maciej W. Rozycki" <macro@...am.me.uk>
To:     Randy Dunlap <rdunlap@...radead.org>
cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        kernel test robot <lkp@...el.com>,
        Paul Burton <paulburton@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org
Subject: Re: [PATCH] mips: DEC: honor CONFIG_MIPS_FP_SUPPORT=n

On Thu, 3 Mar 2022, Randy Dunlap wrote:

> Include the DECstation interrupt handler in opting out of
> FPU support.
> 
> Fixes a linker error:
> 
> mips-linux-ld: arch/mips/dec/int-handler.o: in function `fpu':
> (.text+0x148): undefined reference to `handle_fpe_int'
> 
> Fixes: 183b40f992c8 ("MIPS: Allow FP support to be disabled")
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Reported-by: kernel test robot <lkp@...el.com>
> Cc: Paul Burton <paulburton@...nel.org>
> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> Cc: "Maciej W. Rozycki" <macro@...am.me.uk>
> Cc: linux-mips@...r.kernel.org
> ---
> This builds OK. Is it enough for runtime interrupt handling?

 There's:

#ifdef CONFIG_32BIT
	lw	t2,cpu_fpu_mask
#endif

earlier on that needs to go too, and code in arch/mips/dec/setup.c below:

	/* Register board interrupts: FPU and cascade. */

(we don't want an unhandled interrupt unmasked).  Are you happy to do such 
an update or shall I?

 I cannot verify that change at run time, because any program that does FP 
will then crash.  Maybe init(8) and sulogin(8) won't.  I can check that.

 Thanks for doing this stuff!

  Maciej