ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 32 insertions, 0 deletions

diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig
new file mode 100644
index 000000000..50d2051f7
--- /dev/null
+++ b/drivers/tee/optee/Kconfig
@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# OP-TEE Trusted Execution Environment Configuration
+config OPTEE
+	tristate "OP-TEE"
+	depends on HAVE_ARM_SMCCC
+	depends on MMU
+	depends on RPMB || !RPMB
+	help
+	  This implements the OP-TEE Trusted Execution Environment (TEE)
+	  driver.
+
+config OPTEE_INSECURE_LOAD_IMAGE
+	bool "Load OP-TEE image as firmware"
+	default n
+	depends on OPTEE && ARM64
+	help
+	  This loads the BL32 image for OP-TEE as firmware when the driver is
+	  probed. This returns -EPROBE_DEFER until the firmware is loadable from
+	  the filesystem which is determined by checking the system_state until
+	  it is in SYSTEM_RUNNING. This also requires enabling the corresponding
+	  option in Trusted Firmware for Arm. The documentation there explains
+	  the security threat associated with enabling this as well as
+	  mitigations at the firmware and platform level.
+	  https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
+
+	  Additional documentation on kernel security risks are at
+	  Documentation/tee/op-tee.rst.
+
+config OPTEE_STATIC_PROTMEM_POOL
+	bool
+	depends on HAS_IOMEM && TEE_DMABUF_HEAPS
+	default y