linux-kernel - Re: [PATCH 0/2 RESEND v7] add reserved e820 ranges to the kdump kernel e820 table

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Message-ID: <20181126180455.GI4843@zn.tnic>
Date:   Mon, 26 Nov 2018 19:04:55 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Lianbo Jiang <lijiang@...hat.com>, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org, x86@...nel.org,
        linux-ia64@...r.kernel.org, linux-efi@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org,
        dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        ard.biesheuvel@...aro.org, tony.luck@...el.com,
        fenghua.yu@...el.com, dyoung@...hat.com, bhe@...hat.com
Subject: Re: [PATCH 0/2 RESEND v7] add reserved e820 ranges to the kdump
 kernel e820 table

On Mon, Nov 26, 2018 at 09:44:46AM -0800, Dave Hansen wrote:
> On 11/23/18 9:12 PM, Lianbo Jiang wrote:
> > These patches add the new I/O resource descriptor 'IORES_DESC_RESERVED'
> > for the iomem resources search interfaces, and in order to make it still
> > work after the new descriptor is added, these codes originally related
> > to 'IORES_DESC_NONE' have been updated.
> 
> I'm having a really hard time figuring out what problem these patches solve.
> 
> What end-user visible behavior does this set change?

Yeah, that was a long process of digging out the "why".

I'd recommend reading the previous threads and, more specifically:

https://lkml.kernel.org/r/CABhMZUUscS3jUZUSM5Y6EYJK6weo7Mjj5-EAKGvbw0qEe%2B38zw@mail.gmail.com

in short: we need to export e820 reserved ranges to the second kernel so
that it can talk to PCI devices properly. (And I'm wondering how it did
work until now...)

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.