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From:   Martin Fernandez <martin.fernandez@eclypsium.com>
Date:   Tue, 5 Jul 2022 14:35:18 -0300
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Subject: Re: [PATCH v9 9/9] drivers/node: Show in sysfs node's crypto capabilities
To:     Greg KH <gregkh@linuxfoundation.org>
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On 7/4/22, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Mon, Jul 04, 2022 at 10:58:33AM -0300, Martin Fernandez wrote:
>> Show in each node in sysfs if its memory is able to do be encrypted by
>> the CPU; on EFI systems: if all its memory is marked with
>> EFI_MEMORY_CPU_CRYPTO in the EFI memory map.
>>
>> Signed-off-by: Martin Fernandez <martin.fernandez@eclypsium.com>
>> ---
>>  Documentation/ABI/testing/sysfs-devices-node | 10 ++++++++++
>>  drivers/base/node.c                          | 10 ++++++++++
>>  2 files changed, 20 insertions(+)
>>  create mode 100644 Documentation/ABI/testing/sysfs-devices-node
>>
>> diff --git a/Documentation/ABI/testing/sysfs-devices-node
>> b/Documentation/ABI/testing/sysfs-devices-node
>> new file mode 100644
>> index 000000000000..0e95420bd7c5
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-devices-node
>> @@ -0,0 +1,10 @@
>> +What:		/sys/devices/system/node/nodeX/crypto_capable
>> +Date:		April 2022
>> +Contact:	Martin Fernandez <martin.fernandez@eclypsium.com>
>> +Users:		fwupd (https://fwupd.org)
>> +Description:
>> +		This value is 1 if all system memory in this node is
>> +		capable of being protected with the CPU's memory
>> +		cryptographic capabilities.  It is 0 otherwise.
>> +		On EFI systems the node will be marked with
>> +		EFI_MEMORY_CPU_CRYPTO.
>
> Where will such a node be "marked"?  I do not understand this last
> sentence, sorry, can you please reword this?

What I meant is that if all the memory regions in a given node are
flagged with EFI_MEMORY_CPU_CRYPTO then that file will hold a 1.

Maybe it's a little confusing if you don't know what
EFI_MEMORY_CPU_CRYPTO is.

> And why is EFI an issue here at all?

Checking for EFI_MEMORY_CPU_CRYPTO is the way to know if a memory
region is able to be encrypted by the CPU on EFI platforms. It's not
really an issue and it's currently the only implementation for this
file.

Is it clearer here?

  This value is 1 if the memory in this node is capable of being
  protected with the CPU's memory cryptographic capabilities.  It is 0
  otherwise.
  On EFI systems this means that all the memory regions of the node
  have the EFI_MEMORY_CPU_CRYPTO attribute set.

> thanks,
>
> greg k-h
>