Subject: Re: [1/2] powerpc/crashdump: Fix issues with kexec and 36bit physical addr

From: Matthew McClintock <[email-masked]>
Date: Thu, 08 Jul 2010 09:27:15 -0500

On Thu, 2010-07-08 at 04:07 -0500, Milton Miller wrote:
> On Wed, 07 Jul 2010 around 10:51:20 -0000 Matthew McClintock wrote:
> > 
> > Fix sizes of variables so correct values are exported via /proc.
> > Cast variable in comparison to avoid compiler error.
> > 
> > Signed-off-by: Matthew McClintock <[email-masked]>
> > 
> >  
> > -	csize = min(csize, PAGE_SIZE);
> > +	csize = min(csize, (size_t)PAGE_SIZE);
> 
> no use min_t

Ok

> 
> >  
> > -	if (pfn < max_pfn) {
> > +	if ((min_low_pfn < pfn) && (pfn < max_pfn)) {
> >  		vaddr = __va(pfn << PAGE_SHIFT);
> >  		csize = copy_oldmem_vaddr(vaddr, buf, csize, offset, userbuf);
> >  	} else {
> > diff --git a/arch/powerpc/kernel/machine_kexec.c b/arch/powerpc/kernel/machine_kexec.c
> > index bb3d893..ec7f054 100644
> > --- a/arch/powerpc/kernel/machine_kexec.c
> > +++ b/arch/powerpc/kernel/machine_kexec.c
> > @@ -145,6 +145,7 @@ int overlaps_crashkernel(unsigned long start, unsigned long size)
> >  
> >  /* Values we need to export to the second kernel via the device tree. */
> >  static unsigned long kernel_end;
> > +static unsigned long crashk_start;
> >  static unsigned long crashk_size;
> >  
> >  static struct property kernel_end_prop = {
> > @@ -156,7 +157,7 @@ static struct property kernel_end_prop = {
> >  static struct property crashk_base_prop = {
> >  	.name = "linux,crashkernel-base",
> >  	.length = sizeof(unsigned long),
> > -	.value = &crashk_res.start,
> > +	.value = &crashk_start,
> >  };
> >  
> 
> This is wrong, its truncating the start and size.
> 
> Change the variables to be physaddr_t and the length to be sizeof(physaddr_t).
> 
> Since these properites only contain one variable, the number of cells
> can be inferred from the property size like we do for reading the initrd-size.
> 
> Technically they should be an array of be32 but we can make that a comment.

I don't disagree but this can break kexec if phys_addr_t != unsigned
long. Also, doesn't the crash kernel have to live below 2GB so unsigned
long is always fine?

Will still change unless I hear otherwise.

> 
> By the way, why does 32 bit care about the running kernel's size? aka
> linux,kernel-end?  64 bit book 3S needs it because we use mmu hooks
> to copy the pages to their destination, but I thought ppc32 was using
> a relocatable copy routine.  Are we missing the code to create
> temp ref tlbs on the fly for book 3E?

This is not really in this patch or did I miss something? Kexec uses
kernel-end just to add as a invalid region. Not crucial though for 32
bit.

> 
> >  static struct property crashk_size_prop = {
> > @@ -180,6 +181,7 @@ static void __init export_crashk_values(struct device_node *node)
> >  		prom_remove_property(node, prop);
> >  
> >  	if (crashk_res.start != 0) {
> > +		crashk_start = crashk_res.start;
> >  		prom_add_property(node, &crashk_base_prop);
> >  		crashk_size = crashk_res.end - crashk_res.start + 1;
> >  		prom_add_property(node, &crashk_size_prop);
> 
> I guess we use the reuse of the resources varables, but such is
> common code vs userspace.
> 
> milton