From 1aca9a5f7d5a1ef9ee0233eac0fccc77ea6f0626 Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Tue, 23 Jun 2015 17:34:35 +0100 Subject: [PATCH] Only try and read a VMDescription if it should be there The VMDescription section maybe after the EOF mark, the current code does a 'qemu_get_byte' and either gets the header byte identifying the description or an error (which it ignores). Doing the 'get' upsets RDMA which hangs on old machine types without the VMDescription. Just avoid reading the VMDescription if we wouldn't send it. Signed-off-by: Dr. David Alan Gilbert Signed-off-by: Juan Quintela --- migration/savevm.c | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) diff --git a/migration/savevm.c b/migration/savevm.c index 9e0e286797..1a9b00b320 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -1127,16 +1127,35 @@ int qemu_loadvm_state(QEMUFile *f) * Try to read in the VMDESC section as well, so that dumping tools that * intercept our migration stream have the chance to see it. */ - if (qemu_get_byte(f) == QEMU_VM_VMDESCRIPTION) { - uint32_t size = qemu_get_be32(f); - uint8_t *buf = g_malloc(0x1000); - - while (size > 0) { - uint32_t read_chunk = MIN(size, 0x1000); - qemu_get_buffer(f, buf, read_chunk); - size -= read_chunk; + + /* We've got to be careful; if we don't read the data and just shut the fd + * then the sender can error if we close while it's still sending. + * We also mustn't read data that isn't there; some transports (RDMA) + * will stall waiting for that data when the source has already closed. + */ + if (should_send_vmdesc()) { + uint8_t *buf; + uint32_t size; + section_type = qemu_get_byte(f); + + if (section_type != QEMU_VM_VMDESCRIPTION) { + error_report("Expected vmdescription section, but got %d", + section_type); + /* + * It doesn't seem worth failing at this point since + * we apparently have an otherwise valid VM state + */ + } else { + buf = g_malloc(0x1000); + size = qemu_get_be32(f); + + while (size > 0) { + uint32_t read_chunk = MIN(size, 0x1000); + qemu_get_buffer(f, buf, read_chunk); + size -= read_chunk; + } + g_free(buf); } - g_free(buf); } cpu_synchronize_all_post_init(); -- 2.11.4.GIT