linux-kernel - Re: [PATCH] mm/memremap.c: map FS

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Message-ID: <0cbbe205-4573-2dce-14bf-f07c117ac7af@amd.com>
Date:   Thu, 3 Nov 2022 08:55:40 +0100
From:   "Gupta, Pankaj" <pankaj.gupta@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        dan.j.williams@...el.com, thomas.lendacky@....com
Subject: Re: [PATCH] mm/memremap.c: map FS_DAX device memory as decrypted

Hi Andrew,

>> virtio_pmem use devm_memremap_pages() to map the device memory.
>> By default this memory is mapped as encrypted with SEV. Guest
>> reboot changes the current encryption key and guest no longer
>> properly decrypts the FSDAX device meta data.
>>
>> Mark the corresponding device memory region for FSDAX devices
>> (mapped with memremap_pages) as decrypted to retain the persistent
>> memory property.
>>
>> ...
>>
>> --- a/mm/memremap.c
>> +++ b/mm/memremap.c
>> @@ -335,6 +335,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
>>   			WARN(1, "File system DAX not supported\n");
>>   			return ERR_PTR(-EINVAL);
>>   		}
>> +		params.pgprot = pgprot_decrypted(params.pgprot);
>>   		break;
>>   	case MEMORY_DEVICE_GENERIC:
>>   		break;
> 
> Should this be backported into earlier kernels?

Yes, kernel >= 5.10 for clean back-port as it contains the below commit.

> 
> Is b7b3c01b19159 a suitable Fixes: target?

Not very sure. But seems like the right commit for fixes tag as the 
target code is moved in this commit with multiple range support addition.

Should I send a v2 with fixes & stable kernel fixes tag?

Thanks,
Pankaj