linux-kernel - Re: [PATCH v6 14/14] x86: kdebugfs do not use __va for getting setup

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Message-ID: <20131217062417.GE6751@dhcp-16-126.nay.redhat.com>
Date:	Tue, 17 Dec 2013 14:24:17 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	x86@...nel.org, mjg59@...f.ucam.org, hpa@...or.com,
	James.Bottomley@...senPartnership.com, vgoyal@...hat.com,
	ebiederm@...ssion.com, horms@...ge.net.au,
	kexec@...ts.infradead.org, bp@...en8.de, greg@...ah.com,
	toshi.kani@...com, akpm@...ux-foundation.org, mingo@...nel.org,
	msalter@...hat.com, leif.lindholm@...aro.org
Subject: Re: [PATCH v6 14/14] x86: kdebugfs do not use __va for getting
 setup_data virt addr

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@...hat.com>
> > ---
> >  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
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