linux-kernel - Re: [PATCH 1/2 v6] x86/kexec_file: add e820 entry in case e820 type string matches to io resource name

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Date:   Tue, 20 Nov 2018 12:07:18 +0800
From:   lijiang <lijiang@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, x86@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, akpm@...ux-foundation.org, dyoung@...hat.com,
        bhe@...hat.com
Subject: Re: [PATCH 1/2 v6] x86/kexec_file: add e820 entry in case e820 type
 string matches to io resource name

在 2018年11月18日 19:52, Borislav Petkov 写道:
> On Fri, Nov 16, 2018 at 11:25:55AM +0800, lijiang wrote:
>> For the pci mmconfig issue, it should be good enough that the e820 reserved region
>> [mem 0x0000000078000000-0x000000008fffffff] is only passed to the second kernel, but
>> the pci mmconfig region is not the same in another machine.
> 
> Yes. And now the question is, *which* reserved regions need to be mapped
> for the second kernel to function properly? How do we figure that out?
> 
>> A simple case, hotplug a pci network card and use the ssh/nfs to dump the vmcore.
>> If the pci mmconfig region is not reserved in kdump kernel, the pci hotplug device
>> could not be recognized. So the pci network card won't work.
> 
> Yes that's a good example; put *that* example in your commit message.
> 
>> Here, there is an example about SME kdump. Maybe it can help to better understand.
> 
> You keep pasting that and I've read it already. And you keep repeating
> that the reserved regions need to be mapped in the second kernel and I'm
> asking, how do we determine *which* regions should we pass to the second
> kernel?
> 
> If we should pass *all* reserved regions, why?
> 
> IOW, I'm looking for the *why* first.
> 
> Thx.
> 

I guess you have gotten the answer what you want from Dave's reply.

Thank you, Boris. Also thanks for Dave's explanation in detail.

Regards,
Lianbo