[PATCH v2 2/4] x86/vmware: Log kmsg dump on panic

[Alexey Makhalov <alexey.makhalov@broadcom.com>]

Improve debugability of VMware Linux guests by dumping
kernel messages during a panic to VM log file (vmware.log).

Co-developed-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Bo Gan <bo.gan@broadcom.com>
Signed-off-by: Alexey Makhalov <alexey.makhalov@broadcom.com>
---
 arch/x86/include/asm/vmware.h |   1 +
 arch/x86/kernel/cpu/vmware.c  | 132 ++++++++++++++++++++++++++++++++++
 2 files changed, 133 insertions(+)

diff --git a/arch/x86/include/asm/vmware.h b/arch/x86/include/asm/vmware.h
index 6a084e088b30..c23164503e54 100644
--- a/arch/x86/include/asm/vmware.h
+++ b/arch/x86/include/asm/vmware.h
@@ -93,6 +93,7 @@
 #define VMWARE_HYPERVISOR_MAGIC		0x564d5868U
 
 #define VMWARE_CMD_GETVERSION		10
+#define VMWARE_CMD_MESSAGE		30
 #define VMWARE_CMD_GETHZ		45
 #define VMWARE_CMD_GETVCPU_INFO		68
 #define VMWARE_CMD_STEALCLOCK		91
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index 93acd3414e37..9955f2ea0c84 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -30,6 +30,7 @@
 #include <linux/reboot.h>
 #include <linux/static_call.h>
 #include <linux/sched/cputime.h>
+#include <linux/kmsg_dump.h>
 #include <asm/div64.h>
 #include <asm/x86_init.h>
 #include <asm/hypervisor.h>
@@ -211,6 +212,13 @@ static unsigned long vmware_get_tsc_khz(void)
 	return vmware_tsc_khz;
 }
 
+static void kmsg_dumper_vmware_log(struct kmsg_dumper *dumper,
+				   struct kmsg_dump_detail *detail);
+
+static struct kmsg_dumper kmsg_dumper = {
+	.dump = kmsg_dumper_vmware_log
+};
+
 #ifdef CONFIG_PARAVIRT
 static struct cyc2ns_data vmware_cyc2ns __ro_after_init;
 static bool vmw_sched_clock __initdata = true;
@@ -535,6 +543,8 @@ static void __init vmware_platform_setup(void)
 #endif
 
 	vmware_set_capabilities();
+
+	kmsg_dump_register(&kmsg_dumper);
 }
 
 static u8 __init get_hypercall_mode(void)
@@ -630,3 +640,125 @@ const __initconst struct hypervisor_x86 x86_hyper_vmware = {
 	.runtime.sev_es_hcall_finish	= vmware_sev_es_hcall_finish,
 #endif
 };
+
+#define VMWARE_HB_CMD_MESSAGE	0
+#define MESSAGE_STATUS_SUCCESS	(0x01 << 16)
+#define MESSAGE_STATUS_CPT	(0x10 << 16)
+#define MESSAGE_STATUS_HB	(0x80 << 16)
+
+#define RPCI_PROTOCOL_NUM	0x49435052 /* 'RPCI' */
+#define GUESTMSG_FLAG_COOKIE	0x80000000
+
+#define MESSAGE_TYPE_OPEN	(0 << 16)
+#define MESSAGE_TYPE_SENDSIZE	(1 << 16)
+#define MESSAGE_TYPE_SEND	(2 << 16)
+#define MESSAGE_TYPE_CLOSE	(6 << 16)
+
+struct vmw_msg {
+	u32 id;
+	u32 cookie_high;
+	u32 cookie_low;
+};
+
+static int
+vmware_log_open(struct vmw_msg *msg)
+{
+	u32 info;
+
+	vmware_hypercall6(VMWARE_CMD_MESSAGE | MESSAGE_TYPE_OPEN,
+			  RPCI_PROTOCOL_NUM | GUESTMSG_FLAG_COOKIE,
+			  0, &info, &msg->id, &msg->cookie_high,
+			  &msg->cookie_low);
+
+	if ((info & MESSAGE_STATUS_SUCCESS) == 0)
+		return 1;
+
+	msg->id &= 0xffff0000UL;
+	return 0;
+}
+
+static int
+vmware_log_close(struct vmw_msg *msg)
+{
+	u32 info;
+
+	vmware_hypercall5(VMWARE_CMD_MESSAGE | MESSAGE_TYPE_CLOSE, 0, msg->id,
+			  msg->cookie_high, msg->cookie_low, &info);
+
+	if ((info & MESSAGE_STATUS_SUCCESS) == 0)
+		return 1;
+	return 0;
+}
+
+static int
+vmware_log_send(struct vmw_msg *msg, const char *string)
+{
+	u32 info;
+	u32 len = strlen(string);
+
+retry:
+	vmware_hypercall5(VMWARE_CMD_MESSAGE | MESSAGE_TYPE_SENDSIZE, len,
+			  msg->id, msg->cookie_high, msg->cookie_low, &info);
+
+	if (!(info & MESSAGE_STATUS_SUCCESS))
+		return 1;
+
+	/* HB port can't access encrypted memory. */
+	if (!cc_platform_has(CC_ATTR_MEM_ENCRYPT) && (info & MESSAGE_STATUS_HB)) {
+		vmware_hypercall_hb_out(
+			VMWARE_HB_CMD_MESSAGE | MESSAGE_STATUS_SUCCESS,
+			len, msg->id, (uintptr_t) string, msg->cookie_low,
+			msg->cookie_high, &info);
+	} else {
+		do {
+			u32 word;
+			size_t s = min_t(u32, len, sizeof(word));
+
+			memcpy(&word, string, s);
+			len -= s;
+			string += s;
+
+			vmware_hypercall5(VMWARE_CMD_MESSAGE | MESSAGE_TYPE_SEND,
+					  word, msg->id, msg->cookie_high,
+					  msg->cookie_low, &info);
+		} while (len && (info & MESSAGE_STATUS_SUCCESS));
+	}
+
+	if ((info & MESSAGE_STATUS_SUCCESS) == 0) {
+		if (info & MESSAGE_STATUS_CPT)
+			/* A checkpoint occurred. Retry. */
+			goto retry;
+		return 1;
+	}
+	return 0;
+}
+STACK_FRAME_NON_STANDARD(vmware_log_send);
+
+/*
+ * kmsg_dumper_vmware_log - dumps kmsg to vmware.log file on the host
+ */
+static void kmsg_dumper_vmware_log(struct kmsg_dumper *dumper,
+				   struct kmsg_dump_detail *detail)
+{
+	struct vmw_msg msg;
+	struct kmsg_dump_iter iter;
+	static char line[1024];
+	size_t len = 0;
+
+	/* Line prefix to send to VM log file. */
+	line[0] = 'l';
+	line[1] = 'o';
+	line[2] = 'g';
+	line[3] = ' ';
+
+	kmsg_dump_rewind(&iter);
+	while (kmsg_dump_get_line(&iter, true, line + 4, sizeof(line) - 4,
+				  &len)) {
+		line[len + 4] = '\0';
+		if (vmware_log_open(&msg))
+			return;
+		if (vmware_log_send(&msg, line))
+			return;
+		vmware_log_close(&msg);
+	}
+}
-- 
2.43.7