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SubjectRe: [PATCH v9 9/9] drivers/node: Show in sysfs node's crypto capabilities
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

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