From: Alistair Francis <alistair.francis@wdc.com>
Date: Tue, 13 Aug 2024 03:32:51 +0000 (+1000)
Subject: hw/char: riscv_htif: Use blocking qemu_chr_fe_write_all
X-Git-Tag: v9.2.0-rc0~28^2~36
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4a0e8ca322d2a5ec9bdd9409cb02d4c08a07bef6;p=thirdparty%2Fqemu.git

hw/char: riscv_htif: Use blocking qemu_chr_fe_write_all

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 <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20240910045419.1252277-2-alistair.francis@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---

diff --git a/hw/char/riscv_htif.c b/hw/char/riscv_htif.c
index 54fd55c3e6f..0345088e8b3 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);