Don't completely drain the read file descriptor. Instead, only

fill up to the uart's rx fifo size, and leave any remaining input
for when the rx fifo is read. This allows cut'n'paste of long lines
to be done into the bhyve console without truncation.

Also, introduce a mutex since the file input will run in the mevent
thread context and may corrupt state accessed by a vCPU thread.

Reviewed by:	neel
Approved by:	NetApp

1 files changed, 34 insertions, 10 deletions

diff --git a/usr.sbin/bhyve/pci_uart.c b/usr.sbin/bhyve/pci_uart.c
index 3f192e1..dd30551 100644
--- a/usr.sbin/bhyve/pci_uart.c
+++ b/usr.sbin/bhyve/pci_uart.c
@@ -40,6 +40,7 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 #include <stdbool.h>
 #include <string.h>
+#include <pthread.h>
 
 #include "bhyverun.h"
 #include "pci_emul.h"
@@ -97,6 +98,7 @@ struct fifo {
 
 struct pci_uart_softc {
 	struct pci_devinst *pi;
+	pthread_mutex_t mtx;	/* protects all softc elements */
 	uint8_t data;		/* Data register (R/W) */
 	uint8_t ier;		/* Interrupt enable register (R/W) */
 	uint8_t lcr;		/* Line control register (R/W) */
@@ -214,6 +216,13 @@ fifo_numchars(struct fifo *fifo)
 	return (fifo->num);
 }
 
+static int
+fifo_available(struct fifo *fifo)
+{
+
+	return (fifo->num < fifo->size);
+}
+
 static void
 pci_uart_opentty(struct pci_uart_softc *sc)
 {
@@ -304,19 +313,25 @@ pci_uart_drain(int fd, enum ev_type ev, void *arg)
 
 	assert(fd == STDIN_FILENO);
 	assert(ev == EVF_READ);
+	
+	/*
+	 * This routine is called in the context of the mevent thread
+	 * to take out the softc lock to protect against concurrent
+	 * access from a vCPU i/o exit
+	 */
+	pthread_mutex_lock(&sc->mtx);
 
-	while ((ch = ttyread()) != -1) {
-		/*
-		 * If we are in loopback mode then drop this character.
-		 */
-		if ((sc->mcr & MCR_LOOPBACK) != 0)
-			continue;
-
-		if (fifo_putchar(&sc->rxfifo, ch) != 0)
-			sc->lsr |= LSR_OE;
+	if ((sc->mcr & MCR_LOOPBACK) != 0) {
+		(void) ttyread();
+	} else {
+		while (fifo_available(&sc->rxfifo) &&
+		       ((ch = ttyread()) != -1)) {
+			fifo_putchar(&sc->rxfifo, ch);
+		}
+		pci_uart_toggle_intr(sc);
 	}
 
-	pci_uart_toggle_intr(sc);
+	pthread_mutex_unlock(&sc->mtx);
 }
 
 static void
@@ -337,6 +352,8 @@ pci_uart_write(struct vmctx *ctx, int vcpu, struct pci_devinst *pi,
 		pci_uart_opentty(sc);
 		sc->opened = 1;
 	}
+
+	pthread_mutex_lock(&sc->mtx);
 	
 	/*
 	 * Take care of the special case DLAB accesses first
@@ -458,6 +475,7 @@ pci_uart_write(struct vmctx *ctx, int vcpu, struct pci_devinst *pi,
 
 done:
 	pci_uart_toggle_intr(sc);
+	pthread_mutex_unlock(&sc->mtx);
 }
 
 uint64_t
@@ -479,6 +497,8 @@ pci_uart_read(struct vmctx *ctx, int vcpu, struct pci_devinst *pi,
 		sc->opened = 1;
 	}
 
+	pthread_mutex_lock(&sc->mtx);
+
 	/*
 	 * Take care of the special case DLAB accesses first
 	 */
@@ -554,6 +574,8 @@ pci_uart_read(struct vmctx *ctx, int vcpu, struct pci_devinst *pi,
 
 done:
 	pci_uart_toggle_intr(sc);
+	pthread_mutex_unlock(&sc->mtx);
+
 	return (reg);
 }
 
@@ -570,6 +592,8 @@ pci_uart_init(struct vmctx *ctx, struct pci_devinst *pi, char *opts)
 	pi->pi_arg = sc;
 	sc->pi = pi;
 
+	pthread_mutex_init(&sc->mtx, NULL);
+
 	/* initialize config space */
 	pci_set_cfgdata16(pi, PCIR_DEVICE, COM_DEV);
 	pci_set_cfgdata16(pi, PCIR_VENDOR, COM_VENDOR);