Hi Dave,
On Mon, Jul 16, 2018 at 08:24:12PM +0800, Dave Young wrote:
> On 07/16/18 at 12:04pm, James Morse wrote:
> > Hi Dave,
> >
> > On 14/07/18 02:52, Dave Young wrote:
> > > On 07/11/18 at 04:41pm, AKASHI Takahiro wrote:
> > >> Memblock list is another source for usable system memory layout.
> > >> So powerpc's arch_kexec_walk_mem() is moved to kexec_file.c so that
> > >> other memblock-based architectures, particularly arm64, can also utilise
> > >> it. A moved function is now renamed to kexec_walk_memblock() and merged
> > >> into the existing arch_kexec_walk_mem() for general use, either resource
> > >> list or memblock list.
> > >>
> > >> A consequent function will not work for kdump with memblock list, but
> > >> this will be fixed in the next patch.
> >
> > >> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> >
> > >> @@ -513,6 +563,10 @@ static int locate_mem_hole_callback(struct resource *res, void *arg)
> > >> int __weak arch_kexec_walk_mem(struct kexec_buf *kbuf,
> > >> int (*func)(struct resource *, void *))
> > >> {
> > >> + if (IS_ENABLED(CONFIG_HAVE_MEMBLOCK) &&
> > >> + !IS_ENABLED(CONFIG_ARCH_DISCARD_MEMBLOCK))
> > >> + return kexec_walk_memblock(kbuf, func);
> > >
> > > AKASHI, I'm not sure if this works on all arches, for example I chekced
> > > the .config on my Nokia N900 kernel tree, there is HAVE_MEMBLOCK=y and
> > > no CONFIG_ARCH_DISCARD_MEMBLOCK, in 32bit arm code no arch_kexec_walk_mem()
> > By doesn't work you mean it's a change in behaviour?
> > I think this is fine because 32bit arm doesn't support KEXEC_FILE, (this file is
> > kexec_file specific right?).
>
> Ah, replied on a train, I forgot this is only for kexec_file, sorry
> about that. Please ignore the comment.
>
> But since we have a weak function arch_kexec_walk_mem, adding another
> condition branch within this weak function looks not good.
> Something like below would be better:
I see your concern here, but
> int kexec_locate_mem_hole(struct kexec_buf *kbuf)
> {
> int ret;
>
> + if use memblock
> + ret = kexec_walk_memblock()
> + else
> ret = arch_kexec_walk_mem(kbuf, locate_mem_hole_callback);
>
> return ret == 1 ? 0 : -EADDRNOTAVAIL;
> }
what if yet another architecture comes to kexec_file and wanna
take a third approach? How can it override those functions?
Depending on kernel configuration, it might re-define either
kexec_walk_memblock() or arch_kexec_walk_mem(). It sounds weird to me.
Thanks,
-Takahiro AKASHI
>
> >
> > It only affects architectures with MEMBLOCK and KEXEC_FILE: powerpc, s390 and
> > soon arm64. s390 keeps its behaviour because it provides arch_kexec_walk_mem(),
> > and powerpc's is copied in here as its generic 'memblock describes my memory'
> > stuff. The implementation would be the same on arm64, so we're doing this to
> > avoid duplicating otherwise generic arch code. I think 32bit arm should be able
> > to use this too if it gets KEXEC_FILE support. (32bit arms' KEXEC already
> > depends on MEMBLOCK).
> >
> >
> > Thanks,
> >
> > James
>
> Thanks
> Dave
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