Lguest support for Virtio
This makes lguest able to use the virtio devices.
We change the device descriptor page from a simple array to a variable
length "type, config_len, status, config data..." format, and
implement virtio_config_ops to read from that config data.
We use the virtio ring implementation for an efficient Guest <-> Host
virtqueue mechanism, and the new LHCALL_NOTIFY hypercall to kick the
host when it changes.
We also use LHCALL_NOTIFY on kernel addresses for very very early
console output. We could have another hypercall, but this hack works
quite well.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 959aeeb..495e46a 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -55,6 +55,7 @@
#include <linux/clockchips.h>
#include <linux/lguest.h>
#include <linux/lguest_launcher.h>
+#include <linux/virtio_console.h>
#include <asm/paravirt.h>
#include <asm/param.h>
#include <asm/page.h>
@@ -849,6 +850,23 @@
return "LGUEST";
}
+/* Before virtqueues are set up, we use LHCALL_NOTIFY on normal memory to
+ * produce console output. */
+static __init int early_put_chars(u32 vtermno, const char *buf, int count)
+{
+ char scratch[17];
+ unsigned int len = count;
+
+ if (len > sizeof(scratch) - 1)
+ len = sizeof(scratch) - 1;
+ scratch[len] = '\0';
+ memcpy(scratch, buf, len);
+ hcall(LHCALL_NOTIFY, __pa(scratch), 0, 0);
+
+ /* This routine returns the number of bytes actually written. */
+ return len;
+}
+
/*G:050
* Patching (Powerfully Placating Performance Pedants)
*
@@ -1048,6 +1066,9 @@
* adapted for lguest's use. */
add_preferred_console("hvc", 0, NULL);
+ /* Register our very early console. */
+ virtio_cons_early_init(early_put_chars);
+
/* Last of all, we set the power management poweroff hook to point to
* the Guest routine to power off. */
pm_power_off = lguest_power_off;