Re: [libvirt] [PATCH] migrate VMs between different-endian hosts

This patch enables the migration of Qemu VMs between hosts of different endianess. I tested this by migrating a i686 VM between a x86 and ppc64 host.

I am converting the 'int's in the VM's state header to uint32_t assuming this doesn't break compatibility with existing deployments other than Linux. Signed-off-by: Stefan Berger <stefanb(a)linux.vnet.ibm.com&gt; --- src/qemu/qemu_driver.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) Index: libvirt-acl/src/qemu/qemu_driver.c =================================================================== --- libvirt-acl.orig/src/qemu/qemu_driver.c +++ libvirt-acl/src/qemu/qemu_driver.c @@ -43,6 +43,7 @@ #include <sys/wait.h> #include <sys/ioctl.h> #include <sys/un.h> +#include <byteswap.h> #include "qemu_driver.h" @@ -1881,13 +1882,22 @@ VIR_ENUM_IMPL(qemudSaveCompression, QEMU struct qemud_save_header { char magic[sizeof(QEMUD_SAVE_MAGIC)-1]; - int version; - int xml_len; - int was_running; - int compressed; - int unused[15]; + uint32_t version; + uint32_t xml_len; + uint32_t was_running; + uint32_t compressed; + uint32_t unused[15]; }; +static inline void +bswap_header(struct qemud_save_header *hdr) { + hdr->version = bswap_32(hdr->version); + hdr->xml_len = bswap_32(hdr->xml_len); + hdr->was_running = bswap_32(hdr->was_running); + hdr->compressed = bswap_32(hdr->compressed); +} + + /* return -errno on failure, or 0 on success */ static int qemuDomainSaveHeader(int fd, const char *path, char *xml, @@ -3097,6 +3107,11 @@ qemuDomainSaveImageOpen(struct qemud_dri } if (header.version > QEMUD_SAVE_VERSION) { + /* convert endianess and try again */ + bswap_header(&header); + }

+ if (header.version > QEMUD_SAVE_VERSION) { qemuReportError(VIR_ERR_OPERATION_FAILED, _("image version is not supported (%d > %d)"), header.version, QEMUD_SAVE_VERSION);