Re: [libvirt] [PATCH 3/4] Fix QEMU save/restore with block devices

The save process was relying on use of the shell >> append operator to ensure the save data was placed after the libvirt header + XML. This doesn't work for block devices though. Replace this code with use of 'dd' and its 'seek' parameter. The qemuMonitorMigateToCommand() monitor API is used for both save/coredump, and migration via UNIX socket. We can't simply switch this to use 'dd' since this causes problems with the migration usage. Thus, create a dedicated qemuMonitorMigateToFile which can accept an filename + offset, and remove the filename from the current qemuMonitorMigateToCommand() API

+++ b/src/qemu/qemu_driver.c @@ -4789,6 +4789,7 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path, qemuDomainObjPrivatePtr priv; struct stat sb; int is_bdev = 0; + unsigned long long offset;

@@ -1673,7 +1701,8 @@ int qemuMonitorJSONMigrateToCommand(qemuMonitorPtr mon, goto cleanup; } - if (virAsprintf(&dest, "exec:%s >>%s 2>/dev/null", argstr, safe_target) < 0) { + if (virAsprintf(&dest, "exec:%s | dd of=%s seek=%llub", + argstr, safe_target, offset) < 0) {