powerpc/prom_init: Add the ESM call to prom_init

Make the Enter-Secure-Mode (ESM) ultravisor call to switch the VM to secure
mode. Pass kernel base address and FDT address so that the Ultravisor is
able to verify the integrity of the VM using information from the ESM blob.

Add "svm=" command line option to turn on switching to secure mode.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
[ andmike: Generate an RTAS os-term hcall when the ESM ucall fails. ]
Signed-off-by: Michael Anderson <andmike@linux.ibm.com>
[ bauerman: Cleaned up the code a bit. ]
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190820021326.6884-5-bauerman@linux.ibm.com

Documentation/admin-guide/kernel-parameters.txt

@@ -4620,6 +4620,11 @@
 			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
 			is set. Default value is 5.
 
+	svm=		[PPC]
+			Format: { on | off | y | n | 1 | 0 }
+			This parameter controls use of the Protected
+			Execution Facility on pSeries.
+
 	swapaccount=[0|1]
 			[KNL] Enable accounting of swap in memory resource
 			controller if no parameter or 1 is given or disable

arch/powerpc/include/asm/ultravisor-api.h

@@ -25,5 +25,6 @@
 /* opcodes */
 #define UV_WRITE_PATE			0xF104
 #define UV_RETURN			0xF11C
+#define UV_ESM				0xF110
 
 #endif /* _ASM_POWERPC_ULTRAVISOR_API_H */

arch/powerpc/kernel/prom_init.c

@@ -40,6 +40,7 @@
 #include <asm/sections.h>
 #include <asm/machdep.h>
 #include <asm/asm-prototypes.h>
+#include <asm/ultravisor-api.h>
 
 #include <linux/linux_logo.h>
 
@@ -171,6 +172,10 @@ static bool __prombss prom_radix_disable;
 static bool __prombss prom_xive_disable;
 #endif
 
+#ifdef CONFIG_PPC_SVM
+static bool __prombss prom_svm_enable;
+#endif
+
 struct platform_support {
 	bool hash_mmu;
 	bool radix_mmu;
@@ -812,6 +817,17 @@ static void __init early_cmdline_parse(void)
 		prom_debug("XIVE disabled from cmdline\n");
 	}
 #endif /* CONFIG_PPC_PSERIES */
+
+#ifdef CONFIG_PPC_SVM
+	opt = prom_strstr(prom_cmd_line, "svm=");
+	if (opt) {
+		bool val;
+
+		opt += sizeof("svm=") - 1;
+		if (!prom_strtobool(opt, &val))
+			prom_svm_enable = val;
+	}
+#endif /* CONFIG_PPC_SVM */
 }
 
 #ifdef CONFIG_PPC_PSERIES
@@ -1712,6 +1728,43 @@ static void __init prom_close_stdin(void)
 	}
 }
 
+#ifdef CONFIG_PPC_SVM
+static int prom_rtas_hcall(uint64_t args)
+{
+	register uint64_t arg1 asm("r3") = H_RTAS;
+	register uint64_t arg2 asm("r4") = args;
+
+	asm volatile("sc 1\n" : "=r" (arg1) :
+			"r" (arg1),
+			"r" (arg2) :);
+	return arg1;
+}
+
+static struct rtas_args __prombss os_term_args;
+
+static void __init prom_rtas_os_term(char *str)
+{
+	phandle rtas_node;
+	__be32 val;
+	u32 token;
+
+	prom_debug("%s: start...\n", __func__);
+	rtas_node = call_prom("finddevice", 1, 1, ADDR("/rtas"));
+	prom_debug("rtas_node: %x\n", rtas_node);
+	if (!PHANDLE_VALID(rtas_node))
+		return;
+
+	val = 0;
+	prom_getprop(rtas_node, "ibm,os-term", &val, sizeof(val));
+	token = be32_to_cpu(val);
+	prom_debug("ibm,os-term: %x\n", token);
+	if (token == 0)
+		prom_panic("Could not get token for ibm,os-term\n");
+	os_term_args.token = cpu_to_be32(token);
+	prom_rtas_hcall((uint64_t)&os_term_args);
+}
+#endif /* CONFIG_PPC_SVM */
+
 /*
  * Allocate room for and instantiate RTAS
  */
@@ -3168,6 +3221,46 @@ static void unreloc_toc(void)
 #endif
 #endif
 
+#ifdef CONFIG_PPC_SVM
+/*
+ * Perform the Enter Secure Mode ultracall.
+ */
+static int enter_secure_mode(unsigned long kbase, unsigned long fdt)
+{
+	register unsigned long r3 asm("r3") = UV_ESM;
+	register unsigned long r4 asm("r4") = kbase;
+	register unsigned long r5 asm("r5") = fdt;
+
+	asm volatile("sc 2" : "+r"(r3) : "r"(r4), "r"(r5));
+
+	return r3;
+}
+
+/*
+ * Call the Ultravisor to transfer us to secure memory if we have an ESM blob.
+ */
+static void setup_secure_guest(unsigned long kbase, unsigned long fdt)
+{
+	int ret;
+
+	if (!prom_svm_enable)
+		return;
+
+	/* Switch to secure mode. */
+	prom_printf("Switching to secure mode.\n");
+
+	ret = enter_secure_mode(kbase, fdt);
+	if (ret != U_SUCCESS) {
+		prom_printf("Returned %d from switching to secure mode.\n", ret);
+		prom_rtas_os_term("Switch to secure mode failed.\n");
+	}
+}
+#else
+static void setup_secure_guest(unsigned long kbase, unsigned long fdt)
+{
+}
+#endif /* CONFIG_PPC_SVM */
+
 /*
  * We enter here early on, when the Open Firmware prom is still
  * handling exceptions and the MMU hash table for us.
@@ -3366,6 +3459,9 @@ unsigned long __init prom_init(unsigned long r3, unsigned long r4,
 	unreloc_toc();
 #endif
 
+	/* Move to secure memory if we're supposed to be secure guests. */
+	setup_secure_guest(kbase, hdr);
+
 	__start(hdr, kbase, 0, 0, 0, 0, 0);
 
 	return 0;