linux-kernel - Re: [PATCH 0/3 v3] add reserved e820 ranges to the kdump kernel e820 table

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Message-ID: <20181016025657.GB13006@dhcp-128-65.nay.redhat.com>
Date:   Tue, 16 Oct 2018 10:56:57 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Lianbo Jiang <lijiang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, thomas.lendacky@....com,
        bhelgaas@...gle.com, baiyaowei@...s.chinamobile.com, tiwai@...e.de,
        bp@...e.de, brijesh.singh@....com, bhe@...hat.com
Subject: Re: [PATCH 0/3 v3] add reserved e820 ranges to the kdump kernel e820
 table

On 09/21/18 at 03:32pm, Lianbo Jiang wrote:
> E820 reserved ranges is useful in kdump kernel, we have added this in
> kexec-tools code.
> 
> One reason is PCI mmconf (extended mode) requires reserved region otherwise
> it falls back to legacy mode.
> 
> Furthermore, when AMD SME kdump support, it needs to map dmi table area as
> unencrypted. For normal boot, these ranges sit in e820 reserved ranges,
> thus the early ioremap code naturally map them as unencrypted. If we also
> have same e820 reserve setup in kdump kernel then it will just work like
> normal kernel.
> 
> Kdump uses walk_iomem_res_desc to iterate resources, then adds matched desc
> to e820 table for the kdump kernel.
> 
> But IORES_DESC_NONE resource type includes several different e820 types, we
> need add exact e820 type to the kdump kernel e820 table, thus it also needs
> an extra checking in memmap_entry_callback() to match the e820 type and
> resource name.
> 
> By the way, we also fix an error which walks through iomem resources, the
> values of the function parameter may be modified in the while loop of
> __walk_iomem_res_desc(), which will cause us to not get the desired result
> in some cases.
> 
> Changes since v2:
> 1. Modified the value of flags to "0", when walking through the whole
> tree for e820 reserved ranges.
> 2. Modified the invalid SOB chain issue.
> 
> Lianbo Jiang (3):
>   resource: fix an error which walks through iomem resources
>   x86/kexec_file: add e820 entry in case e820 type string matches to io
>     resource name
>   x86/kexec_file: add reserved e820 ranges to kdump kernel e820 table

Lianbo, since Bjorn has fixed the resource issue in another patchset,
can you rebase your patch 2 and 3 on top of his patches and resend?

> 
>  arch/x86/include/asm/e820/api.h |  2 ++
>  arch/x86/kernel/crash.c         | 11 ++++++++++-
>  arch/x86/kernel/e820.c          |  2 +-
>  kernel/resource.c               |  3 +++
>  4 files changed, 16 insertions(+), 2 deletions(-)
> 
> -- 
> 2.17.1
> 

Thanks
Dave