kvm,8250: Fix "too much work for irq4" problems

This patch fixes the "too much work for irq4" problems caused by the fact that
we never set the UART_IIR_NO_INT flag in the emulation layer. This makes the
interrupt handler in the guest kernel process as much as possible which
triggers a warning.

Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/tools/kvm/8250-serial.c b/tools/kvm/8250-serial.c
index 6056ed6b30d0882b0b09d5cbaca762b9d07bfc69..834c523f4cffc87aa8398d17f8334da6ede3950f 100644 (file)
--- a/tools/kvm/8250-serial.c
+++ b/tools/kvm/8250-serial.c
@@ -23,6 +23,8 @@ struct serial8250_device {
        uint8_t                 mcr;
        uint8_t                 lsr;
        uint8_t                 scr;
+
+       uint8_t                 counter;
 };
 
 static struct serial8250_device devices[] = {
@@ -37,11 +39,15 @@ static struct serial8250_device devices[] = {
        [1]     = {
                .iobase                 = 0x2f8,
                .irq                    = 3,
+
+               .iir                    = UART_IIR_NO_INT,
        },
        /* ttyS2 */
        [2]     = {
                .iobase                 = 0x3e8,
                .irq                    = 4,
+
+               .iir                    = UART_IIR_NO_INT,
        },
 };
 
@@ -158,6 +164,11 @@ static bool serial8250_out(struct kvm *self, uint16_t port, void *data, int size
                        }
                        fflush(stdout);
 
+                       if (dev->counter++ > 10) {
+                               dev->iir                = UART_IIR_NO_INT;
+                               dev->counter            = 0;
+                       }
+
                        break;
                }
                case UART_IER:
@@ -200,6 +211,8 @@ static bool serial8250_in(struct kvm *self, uint16_t port, void *data, int size,
        switch (offset) {
        case UART_TX:
                if (dev->lsr & UART_LSR_DR) {
+                       dev->iir                = UART_IIR_NO_INT;
+
                        dev->lsr                &= ~UART_LSR_DR;
                        ioport__write8(data, dev->thr);
                }