| Message ID | 20240815015410.369925-2-alistair.francis@wdc.com |
|---|---|
| State | New |
| Headers | show |
| Series | riscv: char: Avoid dropped charecters | expand |
On 8/14/24 10:54 PM, Alistair Francis wrote: > The current approach of using qemu_chr_fe_write() and ignoring the > return values results in dropped charecters [1]. Ideally we want to > report FIFO status to the guest, but the HTIF isn't a real UART, so we > don't really have a way to do that. > > Instead let's just use qemu_chr_fe_write_all() so at least we don't drop > charecters. > > 1: https://gitlab.com/qemu-project/qemu/-/issues/2114 > > Signed-off-by: Alistair Francis <alistair.francis@wdc.com> > --- Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com> > hw/char/riscv_htif.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/hw/char/riscv_htif.c b/hw/char/riscv_htif.c > index 9bef60def1..d40b542948 100644 > --- a/hw/char/riscv_htif.c > +++ b/hw/char/riscv_htif.c > @@ -218,7 +218,11 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) > tswap64(syscall[3]) == HTIF_CONSOLE_CMD_PUTC) { > uint8_t ch; > cpu_physical_memory_read(tswap64(syscall[2]), &ch, 1); > - qemu_chr_fe_write(&s->chr, &ch, 1); > + /* > + * XXX this blocks entire thread. Rewrite to use > + * qemu_chr_fe_write and background I/O callbacks > + */ > + qemu_chr_fe_write_all(&s->chr, &ch, 1); > resp = 0x100 | (uint8_t)payload; > } else { > qemu_log_mask(LOG_UNIMP, > @@ -237,7 +241,11 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) > return; > } else if (cmd == HTIF_CONSOLE_CMD_PUTC) { > uint8_t ch = (uint8_t)payload; > - qemu_chr_fe_write(&s->chr, &ch, 1); > + /* > + * XXX this blocks entire thread. Rewrite to use > + * qemu_chr_fe_write and background I/O callbacks > + */ > + qemu_chr_fe_write_all(&s->chr, &ch, 1); > resp = 0x100 | (uint8_t)payload; > } else { > qemu_log("HTIF device %d: unknown command\n", device);
diff --git a/hw/char/riscv_htif.c b/hw/char/riscv_htif.c index 9bef60def1..d40b542948 100644 --- a/hw/char/riscv_htif.c +++ b/hw/char/riscv_htif.c @@ -218,7 +218,11 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) tswap64(syscall[3]) == HTIF_CONSOLE_CMD_PUTC) { uint8_t ch; cpu_physical_memory_read(tswap64(syscall[2]), &ch, 1); - qemu_chr_fe_write(&s->chr, &ch, 1); + /* + * XXX this blocks entire thread. Rewrite to use + * qemu_chr_fe_write and background I/O callbacks + */ + qemu_chr_fe_write_all(&s->chr, &ch, 1); resp = 0x100 | (uint8_t)payload; } else { qemu_log_mask(LOG_UNIMP, @@ -237,7 +241,11 @@ static void htif_handle_tohost_write(HTIFState *s, uint64_t val_written) return; } else if (cmd == HTIF_CONSOLE_CMD_PUTC) { uint8_t ch = (uint8_t)payload; - qemu_chr_fe_write(&s->chr, &ch, 1); + /* + * XXX this blocks entire thread. Rewrite to use + * qemu_chr_fe_write and background I/O callbacks + */ + qemu_chr_fe_write_all(&s->chr, &ch, 1); resp = 0x100 | (uint8_t)payload; } else { qemu_log("HTIF device %d: unknown command\n", device);
The current approach of using qemu_chr_fe_write() and ignoring the return values results in dropped charecters [1]. Ideally we want to report FIFO status to the guest, but the HTIF isn't a real UART, so we don't really have a way to do that. Instead let's just use qemu_chr_fe_write_all() so at least we don't drop charecters. 1: https://gitlab.com/qemu-project/qemu/-/issues/2114 Signed-off-by: Alistair Francis <alistair.francis@wdc.com> --- hw/char/riscv_htif.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)