kvm,serial: Implement 16550A FIFO support

This patch implements 16550A FIFO support to the serial console emulation
layer. There's still a bug lurking somewhere which the hypervisor in some busy
loop taking up 100% of CPU. However, this patch is a definite improvement over
the previous hacks.

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

diff --git a/tools/kvm/8250-serial.c b/tools/kvm/8250-serial.c
index f71735a41bda6c10cd7e7273956861b86cc6ce16..44dfd7f9c062f990f159ce048e07419d3a7a736f 100644 (file)
--- a/tools/kvm/8250-serial.c
+++ b/tools/kvm/8250-serial.c
@@ -22,9 +22,8 @@ struct serial8250_device {
        uint8_t                 lcr;
        uint8_t                 mcr;
        uint8_t                 lsr;
+       uint8_t                 msr;
        uint8_t                 scr;
-
-       uint8_t                 counter;
 };
 
 static struct serial8250_device devices[] = {
@@ -34,6 +33,7 @@ static struct serial8250_device devices[] = {
                .irq                    = 4,
 
                .lsr                    = UART_LSR_TEMT | UART_LSR_THRE,
+               .iir                    = UART_IIR_NO_INT,
        },
        /* ttyS1 */
        [1]     = {
@@ -75,9 +75,6 @@ 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;
 
@@ -85,6 +82,9 @@ static void serial8250__receive(struct kvm *self, struct serial8250_device *dev)
        if (c < 0)
                return;
 
+       if (dev->lsr & UART_LSR_DR)
+               dev->lsr        |= UART_LSR_OE;
+
        dev->rbr        = c;
        dev->lsr        |= UART_LSR_DR;
 }
@@ -95,27 +95,17 @@ static void serial8250__receive(struct kvm *self, struct serial8250_device *dev)
 void serial8250__interrupt(struct kvm *self)
 {
        struct serial8250_device *dev = &devices[0];
-       uint8_t new_iir;
-
-       dev->iir        = UART_IIR_NO_INT;
-
-       /* No interrupts enabled. Exit... */
-       if (!(dev->ier & (UART_IER_THRI|UART_IER_RDI)))
-               return;
 
        serial8250__receive(self, dev);
 
-       new_iir         = 0;
-
-       if (dev->lsr & UART_LSR_DR)
-               new_iir                 |= UART_IIR_RDI;
+       if (dev->ier & UART_IER_RDI && dev->lsr & UART_LSR_DR)
+               dev->iir                = UART_IIR_RDI;
        else if (dev->ier & UART_IER_THRI)
-               new_iir                 |= UART_IIR_THRI;
+               dev->iir                = UART_IIR_THRI;
+       else
+               dev->iir                = UART_IIR_NO_INT;
 
-       /* Only send an IRQ if there's work to do. */
-       if (new_iir) {
-               dev->counter            = 0;
-               dev->iir                = new_iir;
+       if (dev->iir != UART_IIR_NO_INT) {
                kvm__irq_line(self, dev->irq, 0);
                kvm__irq_line(self, dev->irq, 1);
        }
@@ -145,36 +135,34 @@ static bool serial8250_out(struct kvm *self, uint16_t port, void *data, int size
 
        offset          = port - dev->iobase;
 
-       /* LSR is factory test and MSR is not used for writes */
-       if (offset == UART_LSR || offset == UART_MSR)
-               return true;
-
-       /* FCR, LCR, MCR, and SCR have the same meaning regardless of DLAB */
-       switch (offset) {
-       case UART_FCR:
-               dev->fcr                = ioport__read8(data);
-               return true;
-       case UART_LCR:
-               dev->lcr                = ioport__read8(data);
-               return true;
-       case UART_MCR:
-               dev->mcr                = ioport__read8(data);
-               return true;
-       case UART_SCR:
-               dev->scr                = ioport__read8(data);
-               return true;
-       default:
-               break;
-       }
-
        if (dev->lcr & UART_LCR_DLAB) {
                switch (offset) {
                case UART_DLL:
-                       dev->dll                = ioport__read8(data);
+                       dev->dll        = ioport__read8(data);
                        break;
                case UART_DLM:
-                       dev->dlm                = ioport__read8(data);
+                       dev->dlm        = ioport__read8(data);
+                       break;
+               case UART_FCR:
+                       dev->fcr        = ioport__read8(data);
+                       break;
+               case UART_LCR:
+                       dev->lcr        = ioport__read8(data);
                        break;
+               case UART_MCR:
+                       dev->mcr        = ioport__read8(data);
+                       break;
+               case UART_LSR:
+                       /* Factory test */
+                       break;
+               case UART_MSR:
+                       /* Not used */
+                       break;
+               case UART_SCR:
+                       dev->scr        = ioport__read8(data);
+                       break;
+               default:
+                       return false;
                }
        } else {
                switch (offset) {
@@ -182,23 +170,41 @@ static bool serial8250_out(struct kvm *self, uint16_t port, void *data, int size
                        char *p = data;
                        int i;
 
-                       while (count--) {
-                               for (i = 0; i < size; i++)
-                                       fprintf(stdout, "%c", *p++);
+                       if (!(dev->mcr & UART_MCR_LOOP)) {
+                               while (count--) {
+                                       for (i = 0; i < size; i++)
+                                               fprintf(stdout, "%c", *p++);
+                               }
+                               fflush(stdout);
                        }
-                       fflush(stdout);
-
-                       if (dev->counter++ > 10)
-                               dev->iir                = UART_IIR_NO_INT;
-
+                       dev->iir                = UART_IIR_NO_INT;
                        break;
                }
+               case UART_FCR:
+                       dev->fcr        = ioport__read8(data);
+                       break;
                case UART_IER:
-                       dev->ier                = ioport__read8(data);
+                       dev->ier        = ioport__read8(data) & 0x3f;
+                       break;
+               case UART_LCR:
+                       dev->lcr        = ioport__read8(data);
+                       break;
+               case UART_MCR:
+                       dev->mcr        = ioport__read8(data);
+                       break;
+               case UART_LSR:
+                       /* Factory test */
+                       break;
+               case UART_MSR:
+                       /* Not used */
+                       break;
+               case UART_SCR:
+                       dev->scr        = ioport__read8(data);
                        break;
+               default:
+                       return false;
                }
        }
-
        return true;
 }
 
@@ -213,7 +219,6 @@ static bool serial8250_in(struct kvm *self, uint16_t port, void *data, int size,
 
        offset          = port - dev->iobase;
 
-       /* DLAB only changes the meaning of the first two registers */
        if (dev->lcr & UART_LCR_DLAB) {
                switch (offset) {
                case UART_DLL:
@@ -222,29 +227,34 @@ static bool serial8250_in(struct kvm *self, uint16_t port, void *data, int size,
                case UART_DLM:
                        ioport__write8(data, dev->dlm);
                        return true;
+               default:
+                       break;
                }
        } else {
                switch (offset) {
                case UART_RX:
-                       if (dev->lsr & UART_LSR_DR) {
-                               dev->iir                = UART_IIR_NO_INT;
-
-                               dev->lsr                &= ~UART_LSR_DR;
-                               ioport__write8(data, dev->rbr);
-                       }
+                       ioport__write8(data, dev->rbr);
+                       dev->lsr                &= ~UART_LSR_DR;
+                       dev->iir                = UART_IIR_NO_INT;
                        return true;
                case UART_IER:
                        ioport__write8(data, dev->ier);
                        return true;
+               default:
+                       break;
                }
        }
 
-       /* All other registers have the same meaning regardless of DLAB */
        switch (offset) {
-       case UART_IIR:
-               dev->iir &= 0x3f; /* no FIFO for 8250 */
-               ioport__write8(data, dev->iir);
+       case UART_IIR: {
+               uint8_t iir = dev->iir;
+
+               if (dev->fcr & UART_FCR_ENABLE_FIFO)
+                       iir             |= 0xc0;
+
+               ioport__write8(data, iir);
                break;
+       }
        case UART_LCR:
                ioport__write8(data, dev->lcr);
                break;
@@ -253,16 +263,17 @@ static bool serial8250_in(struct kvm *self, uint16_t port, void *data, int size,
                break;
        case UART_LSR:
                ioport__write8(data, dev->lsr);
+               dev->lsr                &= ~(UART_LSR_OE|UART_LSR_PE|UART_LSR_FE|UART_LSR_BI);
                break;
        case UART_MSR:
-               ioport__write8(data, UART_MSR_CTS);
+               ioport__write8(data, dev->msr);
                break;
        case UART_SCR:
-               /* No SCR for 8250 */
-               ioport__write8(data, 0);
+               ioport__write8(data, dev->scr);
                break;
+       default:
+               return false;
        }
-
        return true;
 }