linux-kernel - Re: [PATCH 0/2 v4] add reserved e820 ranges to the kdump kernel e820 table

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Message-ID: <20181024065759.GB3094@dhcp-128-65.nay.redhat.com>
Date:   Wed, 24 Oct 2018 14:57:59 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Lianbo Jiang <lijiang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        x86@...nel.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        thomas.lendacky@....com, bhe@...hat.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 0/2 v4] add reserved e820 ranges to the kdump kernel e820
 table

On 10/22/18 at 03:47pm, Lianbo Jiang wrote:
> E820 reserved ranges is useful in kdump kernel, it has been added 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
> decrypted. For normal boot, these ranges sit in e820 reserved ranges, thus
> the early ioremap code naturally map them as decrypted. If it also has 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.
> 
> Changes since v1:
> 1. Modified the value of flags to "0", when walking through the whole
> tree for e820 reserved ranges.
> 
> 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.
> 
> Changes since v3:
> 1. Dropped [PATCH 1/3 v3] resource: fix an error which walks through iomem
>    resources. Please refer to this commit <010a93bf97c7> "resource: Fix
>    find_next_iomem_res() iteration issue"
> 
> Note:
> 1. The patches are made based on this branch:
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
> 
> 2. And you need to apply the follow patch before test kdump file_load,
>    otherwise these patches won't work.
>    commit <010a93bf97c7> "resource: Fix find_next_iomem_res() iteration
>    issue"
> 
> Lianbo Jiang (2):
>   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
> 
>  arch/x86/include/asm/e820/api.h |  2 ++
>  arch/x86/kernel/crash.c         | 10 +++++++++-
>  arch/x86/kernel/e820.c          |  2 +-
>  kernel/resource.c               |  1 +
>  4 files changed, 13 insertions(+), 2 deletions(-)
> 
> -- 
> 2.17.1
> 

Lianbo, thank you for the update, added Andrew in cc.

Acked-by: Dave Young <dyoung@...hat.com>

Thanks
Dave