Fwd: [PATCH 10/12] ppc64: Reroute interrupts from zero + offset to KERNELBASE + offset

[Milton Miller]

Oops put the wrong address on this one for the list.

I also see that the sending address is wrong, please reply to
miltonm at bga.com.  The disadvantages of a multi-domain ISP.

milton

Begin forwarded message:

> From: "Milton D. Miller II" <miltonm at realtime.net>
> Date: August 30, 2005 12:41:20 AM CDT
> To: michael at ellerman.id.au
> Cc: linuxppc64-dev at ozlabs.com
> Subject: Re: [PATCH 10/12] ppc64: Reroute interrupts from zero + 
> offset to KERNELBASE + offset
>
>> From michael at ellerman.id.au  Fri Aug 26 12:53:31 2005
>> From: michael at ellerman.id.au (Michael Ellerman)
>> Date: Fri Aug 26 12:53:42 2005
>> Subject: [PATCH 10/12] ppc64: Reroute interrupts from zero + offset to
>> 	KERNELBASE + offset
>> In-Reply-To: <1125024799.128302.675577398916.qpatch at concordia>
>>
>> Regardless of where the kernel's linked we always get interrupts at 
>> low
>> addresses. This patch creates a trampoline in the first 3 pages of 
>> memory,
>> where interrupts land, and patches those addresses to jump into the 
>> real
>> kernel code at KERNELBASE.
>>
>> We also need to reserve the low pages of memory in prom.c, as well as
>> __pa(KERNELBASE) to __pa(klimit).
>>
>> FIXME, 0x8000 should be a #define.
>
>
> Actually we should reserve 0 to __pa(KERNELBASE) for testing kdump
> environment...
>
> Do we work if the reserve of low memory is not part of the mem= ?
> In kdump, this memory will not be part of the "mem=" line passed to
> the capture kernel.
>
> Why is it 0x8000 for the reserve and 0x3000 for the trampoline?
> Do we know what we expect the trampoline will save?
>
> page 9  is the initial stab (for RS64 and POWER3), or are you using
> the new rearranged low memory patch?
>
>
>
>>
>> Signed-off-by: Michael Ellerman <michael at ellerman.id.au>
>> ---
>>
>>  arch/ppc64/kernel/prom.c  |    5 ++++-
>>  arch/ppc64/kernel/setup.c |   22 ++++++++++++++++++++++
>>  2 files changed, 26 insertions(+), 1 deletion(-)
>>
>> Index: work/arch/ppc64/kernel/setup.c
>> ===================================================================
>> --- work.orig/arch/ppc64/kernel/setup.c
>> +++ work/arch/ppc64/kernel/setup.c
>> @@ -362,6 +362,26 @@ static struct machdep_calls __initdata *
>>  	NULL
>>  };
>>
>> +#ifdef CONFIG_KDUMP_CAPTURE_KERNEL
>> +static void setup_kdump_trampoline(void)
>> +{
>> +	unsigned long i;
>> +	unsigned int *addr;
>> +
>> +	/* XXX this only works if PHYSICAL_START <= 32 MB */
>
> how about an #error ?
>
>> +
>> +	for (i = 0x100; i < 0x3000; i += 8) {
>> +		addr  = (unsigned int *)i;
>> +		*addr++ = 0x60000000; /* nop */
>> +		*addr = 0x48000000 | ((PHYSICAL_START - 1) & 0x03fffffc);
>> +
>> +		asm ("dcbst 0,%0; sync; icbi 0,%0; isync" : : "r" (addr));
>
> every 8 bytes is a bit overkill, but ok.   The -1 should be -4, its the
> instruction target..
>
> Others have commented on the comments for the patching.   The
> trick of doing a nop to extend the range to 32k should be
> explicitly stated.
>
>
> Another approach is to copy pages 0-3 down to pages 0-3 and execute the
> copy there.  It does mean that we can't use relative branchs from there
> to the "main" kernel.
>
>> +	}
>> +}
>> +#else
>> +static inline void setup_kdump_trampoline(void) { }
>> +#endif
>> +
>>  /*
>>   * Early initialization entry point. This is called by head.S
>>   * with MMU translation disabled. We rely on the "feature" of
>> @@ -394,6 +414,8 @@ void __init early_setup(unsigned long dt
>>
>>  	DBG(" -> early_setup()\n");
>>
>> +	setup_kdump_trampoline();
>> +
>>  	/*
>>  	 * Fill the default DBG level (do we want to keep
>>  	 * that old mecanism around forever ?)
>> Index: work/arch/ppc64/kernel/prom.c
>> ===================================================================
>> --- work.orig/arch/ppc64/kernel/prom.c
>> +++ work/arch/ppc64/kernel/prom.c
>> @@ -1241,7 +1241,10 @@ void __init early_init_devtree(void *par
>>  	lmb_enforce_memory_limit();
>>  	lmb_analyze();
>>  	systemcfg->physicalMemorySize = lmb_phys_mem_size();
>> -	lmb_reserve(0, __pa(klimit));
>> +	lmb_reserve(__pa(KERNELBASE), __pa(klimit));
>> +#ifdef CONFIG_KDUMP_CAPTURE_KERNEL
>> +	lmb_reserve(0, 0x8000);	/* Reserve the trampoline */
>> +#endif
>>
>>  	DBG("Phys. mem: %lx\n", systemcfg->physicalMemorySize);
>>
>>
>
> milton
>