* Peter Xu (pet...@redhat.com) wrote:
> If the postcopy down due to some reason, we can always see this on dst:
>
> qemu-system-x86_64: RP: Received invalid message 0x0000 length 0x0000
>
> However in most cases that's not the real issue. The problem is that
> qemu_get_be16() has no way to show whether the returned data is valid or
> not, and we are _always_ assuming it is valid. That's possibly not wise.
>
> The best approach to solve this would be: refactoring QEMUFile interface
> to allow the APIs to return error if there is. However it needs quite a
> bit of work and testing. For now, let's explicitly check the validity
> first before using the data in all places for qemu_get_*().
>
> This patch tries to fix most of the cases I can see. Only if we are with
> this, can we make sure we are processing the valid data, and also can we
> make sure we can capture the channel down events correctly.
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> ---
> migration/migration.c | 5 +++++
> migration/ram.c | 21 +++++++++++++++++----
> migration/savevm.c | 40 ++++++++++++++++++++++++++++++++++++++--
> 3 files changed, 60 insertions(+), 6 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index c0206023d7..eae34d0524 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1708,6 +1708,11 @@ static void *source_return_path_thread(void *opaque)
> header_type = qemu_get_be16(rp);
> header_len = qemu_get_be16(rp);
>
> + if (qemu_file_get_error(rp)) {
> + mark_source_rp_bad(ms);
> + goto out;
> + }
> +
> if (header_type >= MIG_RP_MSG_MAX ||
> header_type == MIG_RP_MSG_INVALID) {
> error_report("RP: Received invalid message 0x%04x length 0x%04x",
> diff --git a/migration/ram.c b/migration/ram.c
> index 021d583b9b..f159c16f6a 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -2696,6 +2696,16 @@ static int ram_load_postcopy(QEMUFile *f)
> uint8_t ch;
>
> addr = qemu_get_be64(f);
> +
> + /*
> + * If qemu file error, we should stop here, and then "addr"
> + * may be invalid
> + */
> + ret = qemu_file_get_error(f);
> + if (ret) {
> + break;
> + }
> +
> flags = addr & ~TARGET_PAGE_MASK;
> addr &= TARGET_PAGE_MASK;
>
> @@ -2776,9 +2786,15 @@ static int ram_load_postcopy(QEMUFile *f)
> error_report("Unknown combination of migration flags: %#x"
> " (postcopy mode)", flags);
> ret = -EINVAL;
> + break;
> + }
> +
> + /* Detect for any possible file errors */
> + if (!ret && qemu_file_get_error(f)) {
> + ret = qemu_file_get_error(f);
> }
>
> - if (place_needed) {
> + if (!ret && place_needed) {
> /* This gets called at the last target page in the host page */
> void *place_dest = host + TARGET_PAGE_SIZE - block->page_size;
>
> @@ -2790,9 +2806,6 @@ static int ram_load_postcopy(QEMUFile *f)
> place_source, block);
> }
> }
> - if (!ret) {
> - ret = qemu_file_get_error(f);
> - }
> }
>
> return ret;
> diff --git a/migration/savevm.c b/migration/savevm.c
> index b7908f62be..8814793255 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -1765,6 +1765,11 @@ static int loadvm_process_command(QEMUFile *f)
> cmd = qemu_get_be16(f);
> len = qemu_get_be16(f);
>
> + /* Check validity before continue processing of cmds */
> + if (qemu_file_get_error(f)) {
> + return qemu_file_get_error(f);
> + }
> +
> trace_loadvm_process_command(cmd, len);
> if (cmd >= MIG_CMD_MAX || cmd == MIG_CMD_INVALID) {
> error_report("MIG_CMD 0x%x unknown (len 0x%x)", cmd, len);
> @@ -1830,6 +1835,7 @@ static int loadvm_process_command(QEMUFile *f)
> */
> static bool check_section_footer(QEMUFile *f, SaveStateEntry *se)
> {
> + int ret;
> uint8_t read_mark;
> uint32_t read_section_id;
>
> @@ -1840,6 +1846,13 @@ static bool check_section_footer(QEMUFile *f,
> SaveStateEntry *se)
>
> read_mark = qemu_get_byte(f);
>
> + ret = qemu_file_get_error(f);
> + if (ret) {
> + error_report("%s: Read section footer failed: %d",
> + __func__, ret);
> + return false;
> + }
> +
> if (read_mark != QEMU_VM_SECTION_FOOTER) {
> error_report("Missing section footer for %s", se->idstr);
> return false;
> @@ -1875,6 +1888,13 @@ qemu_loadvm_section_start_full(QEMUFile *f,
> MigrationIncomingState *mis)
> instance_id = qemu_get_be32(f);
> version_id = qemu_get_be32(f);
>
> + ret = qemu_file_get_error(f);
> + if (ret) {
> + error_report("%s: Failed to read instance/version ID: %d",
> + __func__, ret);
> + return ret;
> + }
> +
> trace_qemu_loadvm_state_section_startfull(section_id, idstr,
> instance_id, version_id);
> /* Find savevm section */
> @@ -1922,6 +1942,13 @@ qemu_loadvm_section_part_end(QEMUFile *f,
> MigrationIncomingState *mis)
>
> section_id = qemu_get_be32(f);
>
> + ret = qemu_file_get_error(f);
> + if (ret) {
> + error_report("%s: Failed to read section ID: %d",
> + __func__, ret);
> + return ret;
> + }
> +
> trace_qemu_loadvm_state_section_partend(section_id);
> QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
> if (se->load_section_id == section_id) {
> @@ -1989,8 +2016,14 @@ static int qemu_loadvm_state_main(QEMUFile *f,
> MigrationIncomingState *mis)
> uint8_t section_type;
> int ret = 0;
>
> - while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
> - ret = 0;
> + while (true) {
> + section_type = qemu_get_byte(f);
> +
> + if (qemu_file_get_error(f)) {
> + ret = qemu_file_get_error(f);
> + break;
> + }
> +
> trace_qemu_loadvm_state_section(section_type);
> switch (section_type) {
> case QEMU_VM_SECTION_START:
> @@ -2014,6 +2047,9 @@ static int qemu_loadvm_state_main(QEMUFile *f,
> MigrationIncomingState *mis)
> goto out;
> }
> break;
> + case QEMU_VM_EOF:
> + /* This is the end of migration */
> + goto out;
> default:
> error_report("Unknown savevm section type %d", section_type);
> ret = -EINVAL;
> --
> 2.14.3
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
