From 4a0e8ca322d2a5ec9bdd9409cb02d4c08a07bef6 Mon Sep 17 00:00:00 2001 From: Alistair Francis Date: Tue, 13 Aug 2024 13:32:51 +1000 Subject: [PATCH] hw/char: riscv_htif: Use blocking qemu_chr_fe_write_all MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The current approach of using qemu_chr_fe_write() and ignoring the return values results in dropped characters [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 characters. 1: https://gitlab.com/qemu-project/qemu/-/issues/2114 Signed-off-by: Alistair Francis Reviewed-by: Daniel Henrique Barboza Reviewed-by: Thomas Huth Reviewed-by: Philippe Mathieu-Daudé Message-ID: <20240910045419.1252277-2-alistair.francis@wdc.com> Signed-off-by: Alistair Francis --- 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 54fd55c3e6..0345088e8b 100644 --- a/hw/char/riscv_htif.c +++ b/hw/char/riscv_htif.c @@ -217,7 +217,11 @@ 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, @@ -236,7 +240,11 @@ 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);