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

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Date:   Tue, 3 Jul 2018 11:39:24 +0200
From:   Borislav Petkov <bp@...en8.de>
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, dyoung@...hat.com,
        kexec@...ts.infradead.org, iommu@...ts.linux-foundation.org,
        bhe@...hat.com
Subject: Re: [PATCH 1/5 V5] Add a function(ioremap_encrypted) for kdump when
 AMD sme enabled

On Tue, Jul 03, 2018 at 10:17:19AM +0800, lijiang wrote:
> for example, the elfcorehdr. In fact, the elfcorehdr and notes

You mean this?

 ssize_t __weak elfcorehdr_read_notes(char *buf, size_t count, u64 *ppos)
 {
-       return read_from_oldmem(buf, count, ppos, 0);
+       return read_from_oldmem(buf, count, ppos, 0, sme_active());

That looks encrypted to me.

> call the same function(read_from_oldmem->ioremap_cache), in this case,
> it is very difficult to properly remap the memory if the caller don't
> care whether the memory is encrypted.

So beef up the logic in __ioremap_caller() to figure out based on the
address whether to access the memory encrypted or not. You can find out
the elfcorehdr address in the capture kernel.

-- 
Regards/Gruss,
    Boris.

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