[Xen-devel] [PATCH v2 3/3] hvc_xen: make early_printk work with HVM guests

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Refactor the existing code in xen_raw_console_write to get the generic
early_printk console work with HVM guests.

Take the opportunity to replace the outb loop with a single outsb call
to reduce the number of vmexit.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 drivers/tty/hvc/hvc_xen.c |   27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index bf787aa..a1c3746 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -605,6 +605,16 @@ static int xen_cons_init(void)
 }
 console_initcall(xen_cons_init);
 
+#ifdef CONFIG_X86
+static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len)
+{
+       if (xen_cpuid_base())
+               outsb(0xe9, str, len);
+}
+#else
+static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len) { }
+#endif
+
 #ifdef CONFIG_EARLY_PRINTK
 static int __init xenboot_setup_console(struct console *console, char *string)
 {
@@ -624,8 +634,10 @@ static void xenboot_write_console(struct console *console, 
const char *string,
        unsigned int linelen, off = 0;
        const char *pos;
 
-       if (!xen_pv_domain())
+       if (!xen_pv_domain()) {
+               xen_hvm_early_write(0, string, len);
                return;
+       }
 
        dom0_write_console(0, string, len);
 
@@ -661,17 +673,10 @@ void xen_raw_console_write(const char *str)
 
        if (xen_domain()) {
                rc = dom0_write_console(0, str, len);
-#ifdef CONFIG_X86
-               if (rc == -ENOSYS && xen_hvm_domain())
-                       goto outb_print;
-
-       } else if (xen_cpuid_base()) {
-               int i;
-outb_print:
-               for (i = 0; i < len; i++)
-                       outb(str[i], 0xe9);
-#endif
+               if (rc != -ENOSYS || !xen_hvm_domain())
+                       return;
        }
+       xen_hvm_early_write(0, str, len);
 }
 
 void xen_raw_printk(const char *fmt, ...)
-- 
1.7.10.4


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