kvm,8250: Cleanup receive emulation

This patch cleans up receive emulation by separating the stdin polling and
reading logic from the interrupt logic. The patch also fixes the interrupt
injection code to inject one type of interrupt at a time.

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

diff --git a/tools/kvm/8250-serial.c b/tools/kvm/8250-serial.c
index 16910e35dc169cf71f01016da5f40b7161d3e0a1..8f66f4bfc039e3fe44f8c2ca702d85136031d8c9 100644 (file)
--- a/tools/kvm/8250-serial.c
+++ b/tools/kvm/8250-serial.c
@@ -13,7 +13,7 @@ struct serial8250_device {
        uint16_t                iobase;
        uint8_t                 irq;
 
-       uint8_t                 thr;
+       uint8_t                 rbr;            /* receive buffer */
        uint8_t                 dll;
        uint8_t                 dlm;
        uint8_t                 iir;
@@ -71,6 +71,24 @@ static bool is_readable(int fd)
        return poll(&pollfd, 1, 0) > 0;
 }
 
+static void serial8250__receive(struct kvm *self, struct serial8250_device *dev)
+{
+       int c;
+
+       if (dev->lsr & UART_LSR_DR)
+               return;
+
+       if (!is_readable(fileno(stdin)))
+               return;
+
+       c               = read_char(fileno(stdin));
+       if (c < 0)
+               return;
+
+       dev->rbr        = c;
+       dev->lsr        |= UART_LSR_DR;
+}
+
 /*
  * Interrupts are injected for ttyS0 only.
  */
@@ -85,24 +103,15 @@ void serial8250__interrupt(struct kvm *self)
        if (!(dev->ier & (UART_IER_THRI|UART_IER_RDI)))
                return;
 
+       serial8250__receive(self, dev);
+
        new_iir         = 0;
 
-       /* We're always good for guest sending data. */
-       if (dev->ier & UART_IER_THRI)
+       if (dev->lsr & UART_LSR_DR)
+               new_iir                 |= UART_IIR_RDI;
+       else if (dev->ier & UART_IER_THRI)
                new_iir                 |= UART_IIR_THRI;
 
-       /* Is there input in stdin to send to the guest? */
-       if (!(dev->lsr & UART_LSR_DR) && is_readable(fileno(stdin))) {
-               int c;
-
-               c                       = read_char(fileno(stdin));
-               if (c >= 0) {
-                       dev->thr                = c;
-                       dev->lsr                |= UART_LSR_DR;
-                       new_iir                 |= UART_IIR_RDI;
-               }
-       }
-
        /* Only send an IRQ if there's work to do. */
        if (new_iir) {
                dev->counter            = 0;
@@ -208,12 +217,12 @@ static bool serial8250_in(struct kvm *self, uint16_t port, void *data, int size,
                return false;
 
        switch (offset) {
-       case UART_TX:
+       case UART_RX:
                if (dev->lsr & UART_LSR_DR) {
                        dev->iir                = UART_IIR_NO_INT;
 
                        dev->lsr                &= ~UART_LSR_DR;
-                       ioport__write8(data, dev->thr);
+                       ioport__write8(data, dev->rbr);
                }
                break;
        case UART_IER: