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Subject: Re: [PATCH 1/5 V5] Add a function(ioremap_encrypted) for kdump when
 AMD sme enabled
To:     Borislav Petkov <bp@alien8.de>
Cc:     linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de,
        hpa@zytor.com, ebiederm@xmission.com, joro@8bytes.org,
        thomas.lendacky@amd.com, dyoung@redhat.com,
        kexec@lists.infradead.org, iommu@lists.linux-foundation.org,
        bhe@redhat.com
References: <20180702072639.10110-1-lijiang@redhat.com>
 <20180702072639.10110-2-lijiang@redhat.com> <20180702101451.GB28730@zn.tnic>
 <4ae1cfb5-0a4b-2aac-2575-024e2c74826f@redhat.com>
 <895db996-febd-d50c-91af-4f1ef3d27bd8@redhat.com>
 <20180703111428.GB5748@zn.tnic>
From:   lijiang <lijiang@redhat.com>
Message-ID: <4fbb843b-9597-a48b-8b6f-00e354b91950@redhat.com>
Date:   Tue, 3 Jul 2018 19:44:40 +0800
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在 2018年07月03日 19:14, Borislav Petkov 写道:
> On Tue, Jul 03, 2018 at 06:58:14PM +0800, lijiang wrote:
>> For kdump, the elf header finally use the crash kernel reserved memory, it is not an old memory.
> 
> Lamme repeat my suggestion:
> 
> So beef up the logic in __ioremap_caller() to figure out based on the
> address whether to access the memory encrypted or not. In general, you
> can deduce, based on the region you're mapping, whether you need to map
> in encrypted or decrypted.
> 
> For example:
> 
>         addr = elfcorehdr_addr;
> 
>         /* Read Elf header */
>         rc = elfcorehdr_read((char *)&ehdr, sizeof(Elf64_Ehdr), &addr);
>         if (rc < 0)
>                 return rc;
> 
> elfcorehdr_addr has that elfcorehdr address. So you can check which address
> you're mapping and do:
> 
> __ioremap_caller:
> 
> ...
> 	prot = __ioremap_compute_prot(...);
> 
> and that __ioremap_compute_prot() function which you will add will have
> all that logic to determine encrypted or not by comparing addresses etc.
> 
> Does that make more sense?
> 
Thank you, Boris. Good idea, I will rethink about this issue and post it again.

Regards,
Lianbo