linux-kernel - Re: [PATCH 1/5 V5] Add a function(ioremap_encrypted) for kdump when AMD sme enabled

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Message-ID: <562d8611-750d-3624-1a1b-df21f39812d6@redhat.com>
Date:   Fri, 20 Jul 2018 17:55:04 +0800
From:   lijiang <lijiang@...hat.com>
To:     Borislav Petkov <bp@...en8.de>, Dave Young <dyoung@...hat.com>
Cc:     bhe@...hat.com, 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
Subject: Re: [PATCH 1/5 V5] Add a function(ioremap_encrypted) for kdump when
 AMD sme enabled

在 2018年07月20日 15:32, Borislav Petkov 写道:
> On Fri, Jul 20, 2018 at 01:23:04PM +0800, Dave Young wrote:
>>> Here, it doesn't need to dump MMIO space of the previous kernel, when the
>>> kdump kernel boot, the MMIO address will be remapped in decryption manners,
>>> but the MMIO address don't belong to the range of the crash reserved memory,
>>> for the kdump kernel, the MMIO space(address) and IOMMU device table(address)
>>> are outside address, whereas, the IOMMU device table is encrypted in the first
>>> kernel, the kdump kernel will need to copy the content of IOMMU device table
>>> from the first kernel when the kdump kernel boot, so the IOMMU device table will
>>> be remapped in encryption manners.
> 
> -ENOFCKINGPARSE
> 
> I believe you're the only one who understands that humongous sentence.Sorry for this.

> How about using a fullstop from time to time. And WTF is "encryption
> manners"?
> 
>>> So some of them require to be remapped in encryption manners, and some(address)
>>> require to be remapped in decryption manners.
> 
>> There could be some misunderstanding here.
> 
> Hell yeah there's a misunderstanding!
> 
> Can you folks first relax, sit down and explain the whole problem in
> *plain* English using *simple* sentences. *Not* like the unparseable
> mess above. Use simple, declaratory sentences and don't even try to
> sound fancy:
> 
> "The first kernel boots. It's memory is encrypted... Now, the second
> kernel boots. It must do A because of B. In order to do A, it needs to
> do C. Because D..."
> 
> And so on. Explain what the problem is first. Then explain the proposed
> solution. Explain *why* it needs to be done this way.
> 
> When you've written your explanation, try to read it as someone who
> doesn't know kdump and *think* hard whether your explanation makes
> sense. If it doesn't, fix it and read it again. Rinse and repeat. Until
> it is clear to unenlightened readers too.
> 
Thanks for your advice, I will rewrite the log and send them again.

> It is about time this hurried throwing of half-baked patches at
> maintainers and seeing what sticks, stops!
>