kvm tools: Send SysRq-P to guest kernel on SIGQUIT

This patch makes SIGQUIT to the host hypervisor send 'SysRq-P' to the guest
kernel via 8250 serial console to make debugging stuck guests easier.

Cc: Asias He <asias.hejun@gmail.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/tools/kvm/8250-serial.c b/tools/kvm/8250-serial.c
index e92ff89ebec5ecbff3d2233faf54acfb5c8c7715..639afb21b32da3f9223dadeb2f085cc06588875a 100644 (file)
--- a/tools/kvm/8250-serial.c
+++ b/tools/kvm/8250-serial.c
@@ -53,6 +53,29 @@ static struct serial8250_device devices[] = {
        },
 };
 
+#define SYSRQ_PENDING_NONE             0
+#define SYSRQ_PENDING_BREAK            1
+#define SYSRQ_PENDING_CMD              2
+
+static int sysrq_pending;
+
+static void serial8250__sysrq(struct kvm *self, struct serial8250_device *dev)
+{
+       switch (sysrq_pending) {
+       case SYSRQ_PENDING_BREAK:
+               dev->lsr        |= UART_LSR_DR | UART_LSR_BI;
+
+               sysrq_pending   = SYSRQ_PENDING_CMD;
+               break;
+       case SYSRQ_PENDING_CMD:
+               dev->rbr        = 'p';
+               dev->lsr        |= UART_LSR_DR;
+
+               sysrq_pending   = SYSRQ_PENDING_NONE;
+               break;
+       }
+}
+
 static void serial8250__receive(struct kvm *self, struct serial8250_device *dev)
 {
        int c;
@@ -60,6 +83,11 @@ static void serial8250__receive(struct kvm *self, struct serial8250_device *dev)
        if (dev->lsr & UART_LSR_DR)
                return;
 
+       if (sysrq_pending) {
+               serial8250__sysrq(self, dev);
+               return;
+       }
+
        if (!term_readable(CONSOLE_8250))
                return;
 
@@ -94,6 +122,11 @@ void serial8250__inject_interrupt(struct kvm *self)
        }
 }
 
+void serial8250__inject_sysrq(struct kvm *self)
+{
+       sysrq_pending   = SYSRQ_PENDING_BREAK;
+}
+
 static struct serial8250_device *find_device(uint16_t port)
 {
        unsigned int i;

diff --git a/tools/kvm/include/kvm/8250-serial.h b/tools/kvm/include/kvm/8250-serial.h
index 73ed078547e1c82ea967cbb786fb74d142f93b2b..7a6d3f31834ae0d40ded9fae316a3d889fffe4d6 100644 (file)
--- a/tools/kvm/include/kvm/8250-serial.h
+++ b/tools/kvm/include/kvm/8250-serial.h
@@ -5,5 +5,6 @@ struct kvm;
 
 void serial8250__init(struct kvm *kvm);
 void serial8250__inject_interrupt(struct kvm *kvm);
+void serial8250__inject_sysrq(struct kvm *kvm);
 
 #endif /* KVM__8250_SERIAL_H */

diff --git a/tools/kvm/main.c b/tools/kvm/main.c
index 6aa2534c3bb6184102fe2670248344e0ccc9a81f..d8f0c09084efc5e51fe73b34f0d64419ef246d45 100644 (file)
--- a/tools/kvm/main.c
+++ b/tools/kvm/main.c
@@ -38,6 +38,7 @@ static void handle_sigint(int sig)
 
 static void handle_sigquit(int sig)
 {
+       serial8250__inject_sysrq(kvm);
        kvm__show_registers(kvm);
        kvm__show_code(kvm);
        kvm__show_page_tables(kvm);