linux-kernel - Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in early_memremap_pgprot

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Date:   Wed, 5 Sep 2018 14:46:58 +0800
From:   Dave Young <dyoung@...hat.com>
To:     lijiang <lijiang@...hat.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
        hpa@...or.com, ebiederm@...ssion.com, joro@...tes.org,
        thomas.lendacky@....com, kexec@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, bhe@...hat.com,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH 2/5 V6] x86/ioremap: strengthen the logic in
 early_memremap_pgprot_adjust() to adjust encryption mask

[snip]
> 
> As previously mentioned, there are also many differences between kexec and kdump. In general,
> kexec needs to look at all of available physical memory, but kdump doesn't need.
> 
> For kexec, kexec-tools will read /sys/firmware/memmap and recreate the e820 ranges for the 2nd
> kernel. If it fails, will use /proc/iomem.
> 
> For kdump, kexec-tools will read /proc/iomem and recreate the e820 ranges for kdump kernel.
> BTW: we can not get the range of persistent memory from /proc/iomem. So e820 ranges don't contain
> the persistent memory in kdump kernel, this is the real reason why i need to strengthen the logic
> of adjusting memory encryption mask.

"persistent memory" is different, I think you meant about some reserved
memory instead

> 
> If kexec-tools also use /sys/firmware/memmap for kdump(like kexec), kdump kernel can also work
> without a fix, but the kexec-tools will have to be modified. Are you sure that you want me to
> fix kexec-tools instead of kernel?

Yes, please fix kexec-tools to pass reserved ranges in e820, you will
not need this patch then.

Thanks
Dave