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authorDaniel P. Berrange <berrange@redhat.com>2016-09-06 14:56:04 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2016-09-13 19:09:42 +0200
commit6ab3fc32ea640026726bc5f9f4db622d0954fb8a (patch)
tree8a48b6bb8d9746936bfc5cf8119e95f68b8f694a /hw/char/digic-uart.c
parent7983e829336f68b6df6952dd4b03493b1486fcf5 (diff)
hw: replace most use of qemu_chr_fe_write with qemu_chr_fe_write_all
The qemu_chr_fe_write method will return -1 on EAGAIN if the chardev backend write would block. Almost no callers of the qemu_chr_fe_write() method check the return value, instead blindly assuming data was successfully sent. In most cases this will lead to silent data loss on interactive consoles, but in some cases (eg RNG EGD) it'll just cause corruption of the protocol being spoken. We unfortunately can't fix the virtio-console code, due to a bug in the Linux guest drivers, which would cause the entire Linux kernel to hang if we delay processing of the incoming data in any way. Fixing this requires first fixing the guest driver to not hold spinlocks while writing to the hvc device backend. Fixes bug: https://bugs.launchpad.net/qemu/+bug/1586756 Signed-off-by: Daniel P. Berrange <berrange@redhat.com> Message-Id: <1473170165-540-4-git-send-email-berrange@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'hw/char/digic-uart.c')
-rw-r--r--hw/char/digic-uart.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/hw/char/digic-uart.c b/hw/char/digic-uart.c
index c7604e6766..e96a9b2d8d 100644
--- a/hw/char/digic-uart.c
+++ b/hw/char/digic-uart.c
@@ -77,6 +77,8 @@ static void digic_uart_write(void *opaque, hwaddr addr, uint64_t value,
switch (addr) {
case R_TX:
if (s->chr) {
+ /* 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);
}
break;