[PATCH v3 23/25] xen: support console_switching between Dom0 and DomUs on ARM

[Stefano Stabellini <sstabellini@kernel.org>]

Today Ctrl-AAA is used to switch between Xen and Dom0. Extend the
mechanism to allow for switching between Xen, Dom0, and any of the
initial DomU created from Xen alongside Dom0 out of information provided
via device tree.

Rename xen_rx to console_rx to match the new behavior.

Clarify existing comment about "notify the guest", making it clear that
it is only about the hardware domain.

Export a function named console_input_domain() to allow others to know
which domains has input at a given time.

Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
CC: andrew.cooper3@citrix.com
CC: George.Dunlap@eu.citrix.com
CC: ian.jackson@eu.citrix.com
CC: jbeulich@suse.com
CC: konrad.wilk@oracle.com
CC: tim@xen.org
CC: wei.liu2@citrix.com
---
Changes in v3:
- only call vpl011 functions ifdef CONFIG_SBSA_VUART_CONSOLE
- add blank line and spaces
- remove xen_rx from print messages
- rename xen_rx to console_rx
- keep switch_serial_input() at boot
- add better comments
- fix existing comment
- add warning if no guests console/uart is available
- add console_input_domain function

Changes in v2:
- only call vpl011_rx_char if the vpl011 has been initialized
---
 xen/drivers/char/console.c | 71 +++++++++++++++++++++++++++++++++++++---------
 xen/include/xen/console.h  |  2 ++
 2 files changed, 60 insertions(+), 13 deletions(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 0f05369..cd4dfb1 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -31,10 +31,13 @@
 #include <xen/early_printk.h>
 #include <xen/warning.h>
 #include <xen/pv_console.h>
+#include <asm/setup.h>
 
 #ifdef CONFIG_X86
 #include <xen/consoled.h>
 #include <asm/guest.h>
+#else
+#include <asm/vpl011.h>
 #endif
 
 /* console: comma-separated list of console outputs. */
@@ -389,30 +392,72 @@ static void dump_console_ring_key(unsigned char key)
     free_xenheap_pages(buf, order);
 }
 
-/* CTRL-<switch_char> switches input direction between Xen and DOM0. */
+/*
+ * CTRL-<switch_char> switches input direction between Xen, Dom0 and
+ * DomUs.
+ */
 #define switch_code (opt_conswitch[0]-'a'+1)
-static int __read_mostly xen_rx = 1; /* FALSE => input passed to domain 0. */
+/*
+ * console_rx=0 => input to xen
+ * console_rx=1 => input to dom0
+ * console_rx=N => input dom(N-1)
+ */
+static int __read_mostly console_rx = 0;
+
+struct domain *console_input_domain(void)
+{
+    return get_domain_by_id(console_rx - 1);
+}
 
 static void switch_serial_input(void)
 {
-    static char *input_str[2] = { "DOM0", "Xen" };
-    xen_rx = !xen_rx;
-    printk("*** Serial input -> %s", input_str[xen_rx]);
+    console_rx++;
+    if ( console_rx == max_init_domid + 2 )
+        console_rx = 0;
+
+    if ( !console_rx )
+        printk("*** Serial input to Xen");
+    else
+        printk("*** Serial input to DOM%d", console_rx - 1);
+
     if ( switch_code )
-        printk(" (type 'CTRL-%c' three times to switch input to %s)",
-               opt_conswitch[0], input_str[!xen_rx]);
+        printk(" (type 'CTRL-%c' three times to switch input)",
+               opt_conswitch[0]);
     printk("\n");
 }
 
 static void __serial_rx(char c, struct cpu_user_regs *regs)
 {
-    if ( xen_rx )
+    if ( console_rx == 0 )
         return handle_keypress(c, regs);
 
-    /* Deliver input to guest buffer, unless it is already full. */
-    if ( (serial_rx_prod-serial_rx_cons) != SERIAL_RX_SIZE )
-        serial_rx_ring[SERIAL_RX_MASK(serial_rx_prod++)] = c;
-    /* Always notify the guest: prevents receive path from getting stuck. */
+    if ( console_rx == 1 )
+    {
+        /* Deliver input to guest buffer, unless it is already full. */
+        if ( (serial_rx_prod - serial_rx_cons) != SERIAL_RX_SIZE )
+            serial_rx_ring[SERIAL_RX_MASK(serial_rx_prod++)] = c;
+    }
+#ifdef CONFIG_SBSA_VUART_CONSOLE
+    else
+    {
+        struct domain *d = get_domain_by_id(console_rx - 1);
+
+        /*
+         * If we have a properly initialized vpl011 console for the
+         * domain, without a full PV ring to Dom0 (in that case input
+         * comes from the PV ring), then send the character to it.
+         */
+        if ( !d->arch.vpl011.backend_in_domain && d->arch.vpl011.xen != NULL )
+            vpl011_rx_char_xen(d, c);
+        else
+            printk("Cannot send chars to Dom%d: no UART available\n",
+                   d->domain_id);
+    }
+#endif
+    /*
+     * Always notify the hardware domain: prevents receive path from
+     * getting stuck.
+     */
     send_global_virq(VIRQ_CONSOLE);
 
 #ifdef CONFIG_X86
@@ -923,7 +968,7 @@ void __init console_endboot(void)
      * a useful 'how to switch' message.
      */
     if ( opt_conswitch[1] == 'x' )
-        xen_rx = !xen_rx;
+        console_rx = 0;
 
     register_keyhandler('w', dump_console_ring_key,
                         "synchronously dump console ring buffer (dmesg)", 0);
diff --git a/xen/include/xen/console.h b/xen/include/xen/console.h
index ea06fd8..2fe3912 100644
--- a/xen/include/xen/console.h
+++ b/xen/include/xen/console.h
@@ -31,6 +31,8 @@ void console_end_sync(void);
 void console_start_log_everything(void);
 void console_end_log_everything(void);
 
+struct domain *console_input_domain(void);
+
 /*
  * Steal output from the console. Returns +ve identifier, else -ve error.
  * Takes the handle of the serial line to steal, and steal callback function.
-- 
1.9.1


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