[PATCH v2 5/8] virt: efi_secret: Transition to the faux device interface

Sudeep Holla
2025-03-18T17:02:37Z

The EFI secret area driver does not require the creation of a platform
device. Originally, this approach was chosen for simplicity when the
driver was first implemented.

With the introduction of the lightweight faux device interface, we now
have a more appropriate alternative. Migrate the driver to utilize the
faux bus, given that the platform device it previously created was not
a real one anyway. This will simplify the code, reducing its footprint
while maintaining functionality.

Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-efi@vger.kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
drivers/firmware/efi/efi.c | 5 -----
drivers/virt/coco/efi_secret/efi_secret.c | 29 ++++++++---------------------
2 files changed, 8 insertions(+), 26 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 8aebc747c65bc1b63d514a50fe6f35a9e3c1af0a..862b7744c28ecc9e5a64bbb3533c34119f50267f 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -465,11 +465,6 @@ static int __init efisubsys_init(void)
if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
efi_debugfs_init();

-#ifdef CONFIG_EFI_COCO_SECRET
- if (efi.coco_secret != EFI_INVALID_TABLE_ADDR)
- platform_device_register_simple("efi_secret", 0, NULL, 0);
-#endif
-
return 0;

err_remove_group:
diff --git a/drivers/virt/coco/efi_secret/efi_secret.c b/drivers/virt/coco/efi_secret/efi_secret.c
index 1864f9f80617e082feb574a15327949972c8cc1e..a60976750bef787c78401bf4569ee5d0c7d2b5f4 100644
--- a/drivers/virt/coco/efi_secret/efi_secret.c
+++ b/drivers/virt/coco/efi_secret/efi_secret.c
@@ -16,7 +16,7 @@
* is the GUID of the secret entry, and its content is the secret data.
*/

-#include <linux/platform_device.h>
+#include <linux/device/faux.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/kernel.h>
@@ -152,17 +152,12 @@ static const struct inode_operations efi_secret_dir_inode_operations = {
.unlink = efi_secret_unlink,
};

-static int efi_secret_map_area(struct platform_device *dev)
+static int efi_secret_map_area(struct faux_device *dev)
{
int ret;
struct efi_secret *s = efi_secret_get();
struct linux_efi_coco_secret_area *secret_area;

- if (efi.coco_secret == EFI_INVALID_TABLE_ADDR) {
- dev_err(&dev->dev, "Secret area address is not available\n");
- return -EINVAL;
- }
-
secret_area = memremap(efi.coco_secret, sizeof(*secret_area), MEMREMAP_WB);
if (secret_area == NULL) {
dev_err(&dev->dev, "Could not map secret area EFI config entry\n");
@@ -191,7 +186,7 @@ static int efi_secret_map_area(struct platform_device *dev)
return ret;
}

-static void efi_secret_securityfs_teardown(struct platform_device *dev)
+static void efi_secret_securityfs_teardown(struct faux_device *dev)
{
struct efi_secret *s = efi_secret_get();
int i;
@@ -210,7 +205,7 @@ static void efi_secret_securityfs_teardown(struct platform_device *dev)
dev_dbg(&dev->dev, "Removed securityfs entries\n");
}

-static int efi_secret_securityfs_setup(struct platform_device *dev)
+static int efi_secret_securityfs_setup(struct faux_device *dev)
{
struct efi_secret *s = efi_secret_get();
int ret = 0, i = 0, bytes_left;
@@ -307,7 +302,7 @@ static void efi_secret_unmap_area(void)
}
}

-static int efi_secret_probe(struct platform_device *dev)
+static int efi_secret_probe(struct faux_device *dev)
{
int ret;

@@ -326,23 +321,15 @@ static int efi_secret_probe(struct platform_device *dev)
return ret;
}

-static void efi_secret_remove(struct platform_device *dev)
+static void efi_secret_remove(struct faux_device *dev)
{
efi_secret_securityfs_teardown(dev);
efi_secret_unmap_area();
}

-static struct platform_driver efi_secret_driver = {
- .probe = efi_secret_probe,
- .remove = efi_secret_remove,
- .driver = {
- .name = "efi_secret",
- },
-};
-
-module_platform_driver(efi_secret_driver);
+module_faux_driver(efi_secret, efi_secret_probe, efi_secret_remove,
+ efi.coco_secret != EFI_INVALID_TABLE_ADDR);

MODULE_DESCRIPTION("Confidential computing EFI secret area access");
MODULE_AUTHOR("IBM");
MODULE_LICENSE("GPL");
-MODULE_ALIAS("platform:efi_secret");

--
2.34.1