[PATCH] ARM: Allow MULTIPLATFORM to select XIP

On Friday 19 February 2016 15:36:23 Chris Brandt wrote:

On 19 Feb 2016, Arnd Bergmann wrote:

quoted

For PHYS_OFFSET, parsing the DT doesn't help at all because we only
need it for XIP_KERNEL (more or less at least) which cannot patch
the kernel image at boot time, so knowing that the address is wrong
also doesn't help you.

	Arnd

OK, at first I was thinking that PHYS_OFFSET was only used early in boot as a pointer to valid RAM before the DT was read (in head.S and head-nommu.S). Hence, you could pass in the pointer in via another CPU register like the DT pointer is passed in.

But, now I see that PHYS_OFFSET is used all over the place as a hard coded #define, hence your comment "which cannot patch the kernel image at boot time"

So, I retract my thought...it has to be configured at build-time (unless of course you turn it into a global variable everywhere...which might be an even bigger mess)

BTW, I've tried removing the patching in CONFIG_PHYS_VIRT and replaced it
with references to __pv_phys_pfn_offset, which surprisingly only grew
.text from 4901692 to 4904300 bytes, so the size overhead of doing this
would be close to zero.

	Arnd