linux-kernel - Re: [PATCH] device-dax: map dax memory as decrypted in CoCo guests

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Message-ID: <462965da-a945-7376-825f-f56e233627c9@amd.com>
Date: Tue, 10 Sep 2024 15:07:43 +0200
From: "Gupta, Pankaj" <pankaj.gupta@....com>
To: Kevin Loughlin <kevinloughlin@...gle.com>
Cc: Dan Williams <dan.j.williams@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Dave Jiang <dave.jiang@...el.com>,
 nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
 linux-kernel@...r.kernel.org, changyuanl@...gle.com, pgonda@...gle.com,
 sidtelang@...gle.com, tytso@....edu, pasha.tatashin@...een.com,
 thomas.lendacky@....com
Subject: Re: [PATCH] device-dax: map dax memory as decrypted in CoCo guests

On 9/10/2024 3:00 PM, Gupta, Pankaj wrote:
> On 8/26/2024 11:35 PM, Kevin Loughlin wrote:
>>> How can I test this? Can I test it with virtio-pmem device?
>>
>> Correct. Assuming the CoCo guest accesses some virtio-pmem device in
>> devdax mode, mmapping() this virtio-pmem device's memory region
>> results in the guest and host reading the same (plaintext) values from
>> the region.
> 
> I tried to test the daxdev with virtio-pmem but getting the below error 
> (just tried without this patch)
> 
> root@...ntu:/home/amd# ndctl list -N
> {
>    "dev":"namespace0.0",
>    "mode":"devdax",
>    "map":"dev",
>    "size":1054867456,
>    "uuid":"c8b15ce6-0c8f-4a1a-ada6-b19a90bdf1bb",
>    "numa_node":0
> }
> 
> root@...ntu:cat /dev/zero | daxio --output=/dev/namespace0.0
> daxio: neither input or output is device dax
> 
> Could you please share the instructions (to test with virtio-pmem or 
> Qemu). If not, still okay.

Ah by mistake pressed entered early.

Just want to see the behavior on a SEV system with daxdev (maybe above 
virtio-pmem or other emulated device) and see how this patch helps.


Best regards,
Pankaj