10.01.2019, 23:14, "Dr. David Alan Gilbert" <dgilb...@redhat.com>: > * Yury Kotov (yury-ko...@yandex-team.ru) wrote: >> RAM migration has a RAMBlock validation stage (flag RAM_SAVE_FLAG_MEM_SIZE). >> In this stage QEMU checks further information about RAMBlock: >> 1. Presence (by idstr), >> 2. Length (trying to resize, when differs), >> 3. Optional page size. >> >> This patch adds a check for RAMBlock's offset. Currently we check it during >> RAM pages loading - every RAM page has an offset in its header. But there >> is a >> case when we don't send RAM pages (see below). >> >> The following commits introduce a capability (ignore-external) to skip some >> RAM blocks from migration. In such case the migration stream contains only >> meta information about RAM blocks to validate them. So, the only way to >> check >> block's offset is to send it explicitly. >> >> Signed-off-by: Yury Kotov <yury-ko...@yandex-team.ru> > > But why check that offsets match? THey aren't supposed to! > Offset's are entirely private to each qemu and they're allowed to be > different; the only requirement is that the length and name of each > RAMBlock matches, then all the operations we do over the migration > stream are relative to the start of the block. >
Yes, you are right. It seems that instead I should check block->mr->addr. > > One example where they are validly different is where you hotplug some > RAM, so for example: > > source qemu > -M 4G > hotplug PCI card > hotplug 2G > > destination qemu > -M 4G > PCI card declared on the command line > extra 2G declared on the command line > > The offsets are different but we can migrate that case fine. > > Dave > >> --- >> migration/ram.c | 15 +++++++++++++-- >> 1 file changed, 13 insertions(+), 2 deletions(-) >> >> diff --git a/migration/ram.c b/migration/ram.c >> index 7e7deec4d8..39629254e1 100644 >> --- a/migration/ram.c >> +++ b/migration/ram.c >> @@ -3171,6 +3171,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque) >> if (migrate_postcopy_ram() && block->page_size != >> qemu_host_page_size) { >> qemu_put_be64(f, block->page_size); >> } >> + qemu_put_be64(f, block->offset); >> } >> >> rcu_read_unlock(); >> @@ -4031,7 +4032,7 @@ static int ram_load(QEMUFile *f, void *opaque, int >> version_id) >> >> seq_iter++; >> >> - if (version_id != 4) { >> + if (version_id < 4) { >> ret = -EINVAL; >> } >> >> @@ -4132,6 +4133,16 @@ static int ram_load(QEMUFile *f, void *opaque, int >> version_id) >> ret = -EINVAL; >> } >> } >> + if (version_id >= 5) { >> + ram_addr_t offset; >> + offset = qemu_get_be64(f); >> + if (block->offset != offset) { >> + error_report("Mismatched RAM block offset %s " >> + "%" PRId64 "!= %" PRId64, >> + id, offset, (uint64_t)block->offset); >> + ret = -EINVAL; >> + } >> + } >> ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG, >> block->idstr); >> } else { >> @@ -4363,5 +4374,5 @@ static SaveVMHandlers savevm_ram_handlers = { >> void ram_mig_init(void) >> { >> qemu_mutex_init(&XBZRLE.lock); >> - register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, &ram_state); >> + register_savevm_live(NULL, "ram", 0, 5, &savevm_ram_handlers, &ram_state); >> } >> -- >> 2.20.1 > -- > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK Regards, Yury