On Mon, 2010-08-02 at 12:42 +0300, Avi Kivity wrote:
> On 08/02/2010 12:06 PM, Avi Kivity wrote:
> > I'm hitting some migration issues merging qemu.git into qemu-kvm.git:
> >
> > 1. Crash in mig_cancel test:
> >
> > (gdb) bt
> > #0 0x0000003a91c83dbb in memcpy () from /lib64/libc.so.6
> > #1 0x000000000049c2ff in qemu_get_buffer (f=0x302d870, buf=<value
> > optimized out>, size1=4096) at /usr/include/bits/string3.h:52
> > #2 0x0000000000409464 in ram_load (f=0x302d870, opaque=<value
> > optimized out>, version_id=4) at
> > /build/home/tlv/akivity/qemu-kvm/arch_init.c:407
> > #3 0x000000000049cb4c in qemu_loadvm_state (f=0x302d870) at
> > savevm.c:1708
> > #4 0x0000000000494169 in process_incoming_migration (f=<value
> > optimized out>) at migration.c:63
> > #5 0x0000000000494517 in tcp_accept_incoming_migration (opaque=<value
> > optimized out>) at migration-tcp.c:163
> > #6 0x000000000041b67e in main_loop_wait (nonblocking=<value optimized
> > out>) at /build/home/tlv/akivity/qemu-kvm/vl.c:1300
> > #7 0x00000000004314e7 in kvm_main_loop () at
> > /build/home/tlv/akivity/qemu-kvm/qemu-kvm.c:1710
> > #8 0x000000000041c67f in main_loop (argc=<value optimized out>,
> > argv=<value optimized out>, envp=<value optimized out>)
> > at /build/home/tlv/akivity/qemu-kvm/vl.c:1340
> > #9 main (argc=<value optimized out>, argv=<value optimized out>,
> > envp=<value optimized out>) at /build/home/tlv/akivity/qemu-kvm/vl.c:3069
> >
> > This is on the incoming side so the test completes successfully, only
> > leaving a core dump to fill my disks.
>
>
> This appears to be
>
> > static inline void *host_from_stream_offset(QEMUFile *f,
> > ram_addr_t offset,
> > int flags)
> > {
> > static RAMBlock *block = NULL;
> > char id[256];
> > uint8_t len;
> >
> > if (flags & RAM_SAVE_FLAG_CONTINUE) {
> > if (!block) {
> > fprintf(stderr, "Ack, bad migration stream!\n");
> > return NULL;
> > }
> >
> > return block->host + offset;
> > }
>
> with block == NULL, if my gdb-fu got a static variable in an inlined
> function examined correctly.
If block == NULL, are you getting the fprintf?
> I don't see any special reason for block to be NULL on a cancelled
> migration. Though perhaps the incoming stream was terminated without us
> noticing, and we're migrating from some random buffer and confusing the
> code?
Yeah, I don't understand that either, block == NULL should only be an
initial state, once we've seen a block it shouldn't happen. Does this
patch solve anything:
http://lists.nongnu.org/archive/html/qemu-devel/2010-07/msg01114.html
I could see this fixing it if the migration was re-attempted after the
cancel.
Alex
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