Re: [PATCH] MIPS: SGI-IP27: Install the cache error vector on every CPU

[Thomas Bogendoerfer <tsbogend@alpha.franken.de>]

On Thu, Oct 22, 2026 at 08:07:47PM +0100, Maciej W. Rozycki wrote:
> On Wed, 21 Oct 2026, Imre Kaloz wrote:
> 
> > diff --git a/arch/mips/sgi-ip27/ip27-smp.c b/arch/mips/sgi-ip27/ip27-smp.c
> > index 62733e049570..0fef66b86959 100644
> > --- a/arch/mips/sgi-ip27/ip27-smp.c
> > +++ b/arch/mips/sgi-ip27/ip27-smp.c
> > @@ -133,6 +135,18 @@ static void ip27_init_cpu(void)
> >  	per_cpu_init();
> >  }
> >  
> > +static void ip27_init_secondary(void)
> > +{
> > +	/*
> > +	 * The hub flips the low 128K of the attribute 0 uncached alias per
> > +	 * CPU slice and the cache error vector is fetched through that alias,
> > +	 * so the copy trap_init() made through TO_UNCAC() only serves slice 0.
> > +	 */
> > +	memcpy((void *)CKSEG1ADDR(0x100), (void *)TO_UNCAC(0x100), 0x80);
> 
>  This just copies instructions between the same physical memory locations, 
> from an XKPHYS mapping to its corresponding KSEG1 mapping, i.e. the bus 

IP27 is special here:

/*
 * IP27 uses the R10000's uncached attribute feature.  Attribute 3 selects
 * uncached memory addressing. Hide the definitions on 32-bit compilation
 * of the compat-vdso code.
 */
#ifdef CONFIG_64BIT
#define HSPEC_BASE              _AC(0x9000000000000000, UL)
#define IO_BASE                 _AC(0x9200000000000000, UL)
#define MSPEC_BASE              _AC(0x9400000000000000, UL)
#define UNCAC_BASE              _AC(0x9600000000000000, UL)
#define CAC_BASE                _AC(0xa800000000000000, UL)
#endif

Hub ASIC uses the extra address bits, so the physiacl address is not the same.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]