linux-kernel - [PATCH] arm64: rsi: Add automatic arm-cca-guest module loading

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Message-ID: <20241029141114.7207-1-jeremy.linton@arm.com>
Date: Tue, 29 Oct 2024 09:11:14 -0500
From: Jeremy Linton <jeremy.linton@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: steven.price@....com,
	suzuki.poulose@....com,
	catalin.marinas@....com,
	will@...nel.org,
	gshan@...hat.com,
	sami.mujawar@....com,
	linux-kernel@...r.kernel.org,
	Jeremy Linton <jeremy.linton@....com>
Subject: [PATCH] arm64: rsi: Add automatic arm-cca-guest module loading

The TSM module provides both guest identification as well as
attestation when a guest is run in CCA mode. Lets assure by creating a
dummy platform device that the module is automatically loaded during
boot. Once it is in place it can be used earlier in the boot process
to say decrypt a LUKS rootfs.

Signed-off-by: Jeremy Linton <jeremy.linton@....com>
---
 arch/arm64/include/asm/rsi.h                    |  2 ++
 arch/arm64/kernel/rsi.c                         | 15 +++++++++++++++
 drivers/virt/coco/arm-cca-guest/arm-cca-guest.c |  7 +++++++
 3 files changed, 24 insertions(+)

diff --git a/arch/arm64/include/asm/rsi.h b/arch/arm64/include/asm/rsi.h
index 188cbb9b23f5..1b14a4c4257a 100644
--- a/arch/arm64/include/asm/rsi.h
+++ b/arch/arm64/include/asm/rsi.h
@@ -10,6 +10,8 @@
 #include <linux/jump_label.h>
 #include <asm/rsi_cmds.h>
 
+#define ARMV9_RSI_PDEV_NAME "arm-cca-dev"
+
 DECLARE_STATIC_KEY_FALSE(rsi_present);
 
 void __init arm64_rsi_init(void);
diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
index 3031f25c32ef..ad963eb12921 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c
@@ -8,6 +8,7 @@
 #include <linux/psci.h>
 #include <linux/swiotlb.h>
 #include <linux/cc_platform.h>
+#include <linux/platform_device.h>
 
 #include <asm/io.h>
 #include <asm/mem_encrypt.h>
@@ -140,3 +141,17 @@ void __init arm64_rsi_init(void)
 	static_branch_enable(&rsi_present);
 }
 
+static struct platform_device rsi_dev = {
+	.name = ARMV9_RSI_PDEV_NAME,
+	.id = -1
+};
+
+static int __init rsi_init(void)
+{
+	if (is_realm_world())
+		if (platform_device_register(&rsi_dev))
+			pr_err("failed to register rsi platform device");
+	return 0;
+}
+
+arch_initcall(rsi_init)
diff --git a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c b/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
index 488153879ec9..e7ef3b83d5d9 100644
--- a/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
+++ b/drivers/virt/coco/arm-cca-guest/arm-cca-guest.c
@@ -6,6 +6,7 @@
 #include <linux/arm-smccc.h>
 #include <linux/cc_platform.h>
 #include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
 #include <linux/module.h>
 #include <linux/smp.h>
 #include <linux/tsm.h>
@@ -219,6 +220,12 @@ static void __exit arm_cca_guest_exit(void)
 }
 module_exit(arm_cca_guest_exit);
 
+static const struct platform_device_id arm_cca_match[] = {
+	{ ARMV9_RSI_PDEV_NAME, 0},
+	{ }
+};
+
+MODULE_DEVICE_TABLE(platform, arm_cca_match);
 MODULE_AUTHOR("Sami Mujawar <sami.mujawar@....com>");
 MODULE_DESCRIPTION("Arm CCA Guest TSM Driver");
 MODULE_LICENSE("GPL");
-- 
2.46.0