diff options
| -rw-r--r-- | hw/char/serial.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/hw/char/serial.c b/hw/char/serial.c index ebcacdc872..8c42d03faf 100644 --- a/hw/char/serial.c +++ b/hw/char/serial.c @@ -350,10 +350,24 @@ static void serial_ioport_write(void *opaque, hwaddr addr, uint64_t val, s->poll_msl = 0; } } - if (s->lsr & UART_LSR_THRE) { + + /* Turning on the THRE interrupt on IER can trigger the interrupt + * if LSR.THRE=1, even if it had been masked before by reading IIR. + * This is not in the datasheet, but Windows relies on it. It is + * unclear if THRE has to be resampled every time THRI becomes + * 1, or only on the rising edge. Bochs does the latter, and Windows + * always toggles IER to all zeroes and back to all ones. But for + * now leave it as it has always been in QEMU. + * + * If IER.THRI is zero, thr_ipending is not used. Set it to zero + * so that the thr_ipending subsection is not migrated. + */ + if ((s->ier & UART_IER_THRI) && (s->lsr & UART_LSR_THRE)) { s->thr_ipending = 1; - serial_update_irq(s); + } else { + s->thr_ipending = 0; } + serial_update_irq(s); } break; case 2: |