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Date:   Wed, 6 Jul 2022 08:38:37 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Martin Fernandez <martin.fernandez@eclypsium.com>
Cc:     linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
        platform-driver-x86@vger.kernel.org, linux-mm@kvack.org,
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        rafael@kernel.org, rppt@kernel.org, akpm@linux-foundation.org,
        daniel.gutson@eclypsium.com, hughsient@gmail.com,
        alex.bazhaniuk@eclypsium.com, alison.schofield@intel.com,
        keescook@chromium.org
Subject: Re: [PATCH v9 9/9] drivers/node: Show in sysfs node's crypto
 capabilities
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References: <20220704135833.1496303-1-martin.fernandez@eclypsium.com>
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On Tue, Jul 05, 2022 at 02:35:18PM -0300, Martin Fernandez wrote:
> 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.

Much better, thanks.

greg k-h