Messages in this thread | | | Date | Sun, 12 Aug 2012 23:32:44 -0400 (EDT) | From | Nicolas Pitre <> | Subject | Re: [PATCH v2 03/22] ARM: use late patch framework for phys-virt patching |
| |
On Sun, 12 Aug 2012, Cyril Chemparathy wrote:
> On 08/11/12 23:03, Nicolas Pitre wrote: > > On Fri, 10 Aug 2012, Cyril Chemparathy wrote: > > > > > -extern unsigned long __pv_phys_offset; > > > -#define PHYS_OFFSET __pv_phys_offset > [...] > > > +#define PHYS_OFFSET __virt_to_phys(PAGE_OFFSET) > > > > What was wrong with the former PHYS_OFFSET = __pv_phys_offset ? > > > > If you really want to have it optimized at run time, you could simply > > use your new stub to patch a mov instruction instead of going through > > __virt_to_phys which uses and add on top of a constant. > > > > The intent was to optimize out the load(s) on references to PHYS_OFFSET, but > is it worth it? If so, we could go with a patched mov (or two) with the > necessary endian fixups. If not, we could revert to __pv_phys_offset loads as > before.
If you want to do better than the load, then you'd better go all the way with the patched move.
> > You also should remove the MODULE_ARCH_VERMAGIC_P2V definitions now that > > the corresponding code is no longer there. > > > > Hmm... > > "rt-patch" needs to be in vermagic to prevent modules built against the new > code from being loaded on older kernels that used the traditional patch code.
Right.
> "p2v" needs to be in there as well, because it should be possible to build > without PATCH_PHYS_VIRT, but with RUNTIME_PATCH as and when there are other > users for this.
That doesn't matter if there are other users. As soon as there is a .init.runtime_patch_table that needs to be processed then "rt-patch" flags it. Whether this is used for PATCH_PHYS_VIRT or other purposes is irrelevant.
However there isn't any pv_table anymore, so "p2v" should go as there is no more code to process those tables if they're ever encountered.
Nicolas
| |