ANDROID: misc: pkvm_smc: Add pKVM SMC filter driver

Add a driver that filters SMCs during running KVM in protected mode.

This patch has the skeleton for the driver and its config, and the
logic is added in next patches.

Bug: 278009271
Bug: 357781595
Change-Id: I76b7f0c1fab49f38700d22a161c7cc92730f81a1
Signed-off-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

drivers/misc/Kconfig

@@ -618,6 +618,15 @@ config MARVELL_CN10K_DPI
 	  To compile this driver as a module, choose M here: the module
 	  will be called mrvl_cn10k_dpi.
 
+config PKVM_SMC_FILTER
+	tristate "pKVM SMC Filter"
+	depends on KVM && ARM64 && m
+	help
+	  Support SMC filtering from hypervisor, through a hardcoded configuration in the
+	  driver, this is intended to be a template and not shipped as is.
+
+	  Say N here unless you know what you are doing.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"

drivers/misc/Makefile

@@ -73,3 +73,4 @@ obj-$(CONFIG_NSM)		+= nsm.o
 obj-$(CONFIG_MARVELL_CN10K_DPI)	+= mrvl_cn10k_dpi.o
 obj-y				+= keba/
 obj-$(CONFIG_UID_SYS_STATS)	+= uid_sys_stats.o
+obj-$(CONFIG_PKVM_SMC_FILTER)  += pkvm-smc/

drivers/misc/pkvm-smc/Makefile

@@ -0,0 +1,15 @@
+ifneq ($(KERNELRELEASE),)
+clean-files := pkvm/hyp.lds pkvm/hyp-reloc.S
+obj-m := pkvm_smc.o
+
+pkvm_smc-y := pkvm-smc.o pkvm/kvm_nvhe.o
+
+$(obj)/pkvm/kvm_nvhe.o: FORCE
+	$(Q)$(MAKE) $(build)=$(obj)/pkvm $(obj)/pkvm/kvm_nvhe.o
+else
+all:
+	make -C $(KDIR) M=$(PWD) modules
+clean:
+	make -C $(KDIR) M=$(PWD) clean
+endif
+

drivers/misc/pkvm-smc/pkvm-smc.c

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 - Google Inc
+ * Author: Mostafa Saleh <smostafa@google.com>
+ * Simple module for pKVM SMC filtering.
+ */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <asm/kvm_pkvm_module.h>
+
+static unsigned long pkvm_module_token;
+int kvm_nvhe_sym(pkvm_smc_filter_hyp_init)(const struct pkvm_module_ops *ops);
+
+static int __init smc_filter_init(void)
+{
+	int ret;
+
+	ret = pkvm_load_el2_module(kvm_nvhe_sym(pkvm_smc_filter_hyp_init),
+				   &pkvm_module_token);
+	if (ret)
+		pr_err("Failed to register pKVM SMC filter: %d\n", ret);
+	else
+		pr_info("pKVM SMC filter registered successfully\n");
+
+	return ret;
+}
+
+module_init(smc_filter_init);
+
+MODULE_AUTHOR("Mostafa Saleh <smostafa@google.com>");
+MODULE_DESCRIPTION("pKVM SMC filter");
+MODULE_LICENSE("GPL v2");

drivers/misc/pkvm-smc/pkvm/Makefile

@@ -0,0 +1,2 @@
+hyp-obj-y := pkvm-smc.o
+include $(srctree)/arch/arm64/kvm/hyp/nvhe/Makefile.module

drivers/misc/pkvm-smc/pkvm/pkvm-smc.c

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 - Google Inc
+ * Author: Mostafa Saleh <smostafa@google.com>
+ * Simple module for pKVM SMC filtering.
+ */
+
+#include <asm/kvm_pkvm_module.h>
+
+int pkvm_smc_filter_hyp_init(const struct pkvm_module_ops *ops)
+{
+	return 0;
+}