On 2/3/2022 10:43, Martin Fernandez wrote:
Show in each node in sysfs if its memory is able to do be encrypted by
the CPU, ie. if all its memory is marked with EFI_MEMORY_CPU_CRYPTO in
the EFI memory map.
Signed-off-by: Martin Fernandez <martin.fernandez@xxxxxxxxxxxxx>
---
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..0d1fd86c9faf
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-node
@@ -0,0 +1,10 @@
+What: /sys/devices/system/node/nodeX/crypto_capable
+Date: February 2022
+Contact: Martin Fernandez <martin.fernandez@xxxxxxxxxxxxx>
+Users: fwupd (https://fwupd.org)
+Description:
+ This value is 1 if all system memory in this node is
+ marked with EFI_MEMORY_CPU_CRYPTO, indicating that the
+ system memory is capable of being protected with the
+ CPU’s memory cryptographic capabilities. It is 0
+ otherwise.
\ No newline at end of file
diff --git a/drivers/base/node.c b/drivers/base/node.c
index 87acc47e8951..dabaed997ecd 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -560,11 +560,21 @@ static ssize_t node_read_distance(struct device *dev,
}
static DEVICE_ATTR(distance, 0444, node_read_distance, NULL);
+static ssize_t crypto_capable_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct pglist_data *pgdat = NODE_DATA(dev->id);
+
+ return sysfs_emit(buf, "%d\n", pgdat->crypto_capable);
As there is interest in seeing these capabilities from userspace, it
seems like a logical time to also expose a `crypto_active` attribute.
Then userspace can make a judgement call if the system supports crypto
memory (`crypto_capable`) and then also whether or not it's been turned
on (`crypto_active`).
`crypto_active` could be detected with some existing support in the
kernel of `mem_encrypt_active()`. This will then work for a variety of
architectures too that offer `mem_encrypt_active()`.
As it stands today the only reliable way to tell from userspace (at
least for AMD's x86 implementation) is by grepping the system log for
the line "AMD Memory Encryption Features active".
+}
+static DEVICE_ATTR_RO(crypto_capable);
+
static struct attribute *node_dev_attrs[] = {
&dev_attr_meminfo.attr,
&dev_attr_numastat.attr,
&dev_attr_distance.attr,
&dev_attr_vmstat.attr,
+ &dev_attr_crypto_capable.attr,
NULL
};
