Re: [PATCH v6 14/14] x86: kdebugfs do not use __va for getting setup_data virt addr

Dave Young
2013-12-17T06:24:17Z

On 12/16/13 at 04:35pm, Matt Fleming wrote:
> On Mon, 16 Dec, at 05:30:35PM, Dave Young wrote:
> > kdump kernel will use memmap=exactmap kernel cmdline, but __va does not
> > work in case memmap=exactmap, so let's always use ioremap_cache.
> >
> > Signed-off-by: Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > ---
> > arch/x86/kernel/kdebugfs.c | 35 +++++++++++------------------------
> > 1 file changed, 11 insertions(+), 24 deletions(-)
>
> Dave, I've no idea why this change is necessary from the commit log. Is
> it required for kexec to function on EFI? Why does __va() not work in
> the memmap=exactmap case?
>

During previous kdump tests I saw panics while reading the setup_data in debugfs.
I thought it is caused by some unmapped addresses. At that time I also reproduced
it by booting the non-kexec kernel with memmap=exact.

Since you are asking about this I'm testing it again but I seems can not
reproduce this problem any more, it's weird.

I should dug more about it and save the panic messages.

So let's drop this patch for now, I will keep an eye on this and address it later
if I can find the problem again.

--
Thanks
Dave