[Xen-devel] [patch 22/26] Xen-paravirt_ops: Add early printk support via hvc console

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Add early printk support via hvc console, enable using
"earlyprintk=xen" on the kernel command line.

From: Gerd Hoffmann <kraxel@xxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>

---
 arch/x86_64/kernel/early_printk.c |    8 ++++++++
 drivers/xen/hvc-console.c         |   24 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

===================================================================
--- a/arch/x86_64/kernel/early_printk.c
+++ b/arch/x86_64/kernel/early_printk.c
@@ -196,6 +196,10 @@ static struct console simnow_console = {
        .flags =        CON_PRINTBUFFER,
        .index =        -1,
 };
+
+#ifdef CONFIG_XEN
+extern struct console xenboot_console;
+#endif
 
 /* Direct interface for emergencies */
 struct console *early_console = &early_vga_console;
@@ -243,6 +247,10 @@ static int __init setup_early_printk(cha
                simnow_init(buf + 6);
                early_console = &simnow_console;
                keep_early = 1;
+#ifdef CONFIG_XEN
+       } else if (!strncmp(buf, "xen", 3)) {
+               early_console = &xenboot_console;
+#endif
        }
 
        if (keep_early)
===================================================================
--- a/drivers/xen/hvc-console.c
+++ b/drivers/xen/hvc-console.c
@@ -133,3 +133,27 @@ module_init(xen_init);
 module_init(xen_init);
 module_exit(xen_fini);
 console_initcall(xen_cons_init);
+
+static void xenboot_write_console(struct console *console, const char *string,
+                                 unsigned len)
+{
+       unsigned int linelen, off = 0;
+       const char *pos;
+
+       while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
+               linelen = pos-string+off;
+               if (off + linelen > len)
+                       break;
+               write_console(0, string+off, linelen);
+               write_console(0, "\r\n", 2);
+               off += linelen + 1;
+       }
+       if (off < len)
+               write_console(0, string+off, len-off);
+}
+
+struct console xenboot_console = {
+       .name           = "xenboot",
+       .write          = xenboot_write_console,
+       .flags          = CON_PRINTBUFFER | CON_BOOT,
+};

-- 


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