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From 58d058f1fe1cc5981c57be8b48d3b2f74f25c0d6 Mon Sep 17 00:00:00 2001
From: Jan Kiszka <jan.kiszka@siemens.com>
Date: Sun, 11 Sep 2016 23:30:04 +0200
Subject: [PATCH] jailhouse: Add simple debug console via the hypervisor
Jailhouse allows explicitly enabled cells to write character-wise
messages to the hypervisor debug console. Make use of this for a
platform-agnostic boot diagnosis channel, specifically for non-root
cells. This also comes with earlycon support.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
(cherry picked from commit 60685bd589aef4972d20724863079edf2039eaa2)
From http://git.kiszka.org/?p=linux.git;a=shortlog;h=refs/heads/queues/jailhouse
---
MAINTAINERS | 1 +
drivers/virt/Kconfig | 11 +++++
drivers/virt/Makefile | 1 +
drivers/virt/jailhouse_dbgcon.c | 103 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 116 insertions(+)
create mode 100644 drivers/virt/jailhouse_dbgcon.c
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8774,6 +8774,7 @@ L: jailhouse-dev@googlegroups.com
S: Maintained
F: arch/x86/kernel/jailhouse.c
F: arch/x86/include/asm/jailhouse_para.h
+F: drivers/virt/jailhouse_dbgcon.c
JC42.4 TEMPERATURE SENSOR DRIVER
M: Guenter Roeck <linux@roeck-us.net>
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -31,5 +31,16 @@ config FSL_HV_MANAGER
4) A kernel interface for receiving callbacks when a managed
partition shuts down.
+config JAILHOUSE_DBGCON
+ tristate "Jailhouse console driver"
+ depends on X86 || ARM || ARM64
+ help
+ The Jailhouse hypervisor provides a simple write-only console for
+ debugging the bootstrap process of its cells. This driver registers
+ a console with the kernel to make use of it.
+
+ Note that Jailhouse has to be configured to permit a cell the usage
+ of the console interface.
+
source "drivers/virt/vboxguest/Kconfig"
endif
--- a/drivers/virt/Makefile
+++ b/drivers/virt/Makefile
@@ -4,4 +4,5 @@
#
obj-$(CONFIG_FSL_HV_MANAGER) += fsl_hypervisor.o
+obj-$(CONFIG_JAILHOUSE_DBGCON) += jailhouse_dbgcon.o
obj-y += vboxguest/
--- /dev/null
+++ b/drivers/virt/jailhouse_dbgcon.c
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Console driver for running over the Jailhouse partitioning hypervisor
+ *
+ * Copyright (c) Siemens AG, 2016-2018
+ *
+ * Authors:
+ * Jan Kiszka <jan.kiszka@siemens.com>
+ */
+
+#include <linux/console.h>
+#include <linux/hypervisor.h>
+#include <linux/module.h>
+#include <linux/serial_core.h>
+#ifdef CONFIG_X86
+#include <asm/alternative.h>
+#endif
+#ifdef CONFIG_ARM
+#include <asm/opcodes-virt.h>
+#endif
+
+#define JAILHOUSE_HC_DEBUG_CONSOLE_PUTC 8
+
+static void hypervisor_putc(char c)
+{
+#if defined(CONFIG_X86)
+ int result;
+
+ asm volatile(
+ ALTERNATIVE(".byte 0x0f,0x01,0xc1", ".byte 0x0f,0x01,0xd9",
+ X86_FEATURE_VMMCALL)
+ : "=a" (result)
+ : "a" (JAILHOUSE_HC_DEBUG_CONSOLE_PUTC), "D" (c)
+ : "memory");
+#elif defined(CONFIG_ARM)
+ register u32 num_res asm("r0") = JAILHOUSE_HC_DEBUG_CONSOLE_PUTC;
+ register u32 arg1 asm("r1") = c;
+
+ asm volatile(
+ __HVC(0x4a48)
+ : "=r" (num_res)
+ : "r" (num_res), "r" (arg1)
+ : "memory");
+#elif defined(CONFIG_ARM64)
+ register u64 num_res asm("x0") = JAILHOUSE_HC_DEBUG_CONSOLE_PUTC;
+ register u64 arg1 asm("x1") = c;
+
+ asm volatile(
+ "hvc #0x4a48\n\t"
+ : "=r" (num_res)
+ : "r" (num_res), "r" (arg1)
+ : "memory");
+#else
+#error Unsupported architecture.
+#endif
+}
+
+static void jailhouse_dbgcon_write(struct console *con, const char *s,
+ unsigned count)
+{
+ while (count > 0) {
+ hypervisor_putc(*s);
+ count--;
+ s++;
+ }
+}
+
+static int __init early_jailhouse_dbgcon_setup(struct earlycon_device *device,
+ const char *options)
+{
+ device->con->write = jailhouse_dbgcon_write;
+ return 0;
+}
+
+EARLYCON_DECLARE(jailhouse, early_jailhouse_dbgcon_setup);
+
+static struct console jailhouse_dbgcon = {
+ .name = "jailhouse",
+ .write = jailhouse_dbgcon_write,
+ .flags = CON_PRINTBUFFER | CON_ANYTIME,
+ .index = -1,
+};
+
+static int __init jailhouse_dbgcon_init(void)
+{
+ if (!jailhouse_paravirt())
+ return -ENODEV;
+
+ register_console(&jailhouse_dbgcon);
+ return 0;
+}
+
+static void __exit jailhouse_dbgcon_exit(void)
+{
+ unregister_console(&jailhouse_dbgcon);
+}
+
+module_init(jailhouse_dbgcon_init);
+module_exit(jailhouse_dbgcon_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Jailhouse debug console driver");
+MODULE_AUTHOR("Jan Kiszka <jan.kiszka@siemens.com>");
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