Re: [PATCH v2 2/4] Support live migration between file-backed memory and anonymous memory.

From: Michael Galaxy <mgalaxy(a)akamai.com&gt; In our environment, we need to convert VMs into a live-update-comptabile configuration "on-the-fly" (via live migration). More specifically: We need to convert between anonymous memory-backed VMs and file-backed memory VMs. So, for this very specific case, this needs to work when host-level PMEM is being enabled. QEMU does not have a problem with this at all, but we need to relax the rules here a bit so that libvirt allows it to go through normally. Signed-off-by: Michael Galaxy <mgalaxy(a)akamai.com&gt; --- src/qemu/qemu_domain.c | 24 +++++++++++++++++++----- 1 file changed, 19 insertions(+), 5 deletions(-) diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index bda62f2e5c..93e98f8dae 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -8641,11 +8641,25 @@ qemuDomainABIStabilityCheck(const virDomainDef *src, size_t i; if (src->mem.source != dst->mem.source) { - virReportError(VIR_ERR_CONFIG_UNSUPPORTED, - _("Target memoryBacking source '%1$s' doesn't match source memoryBacking source'%2$s'"), - virDomainMemorySourceTypeToString(dst->mem.source), - virDomainMemorySourceTypeToString(src->mem.source)); - return false; + /* + * The current use case for this is the live migration of live-update + * capable CPR guests mounted on PMEM devices at the host

+ * level (not in-guest PMEM). QEMU has no problem doing these kinds of + * live migrations between these two memory backends, so let them go through. + * This allows us to "upgrade" guests from regular memory to file-backed + * memory seemlessly without taking them down. + */ + if (!((src->mem.source == VIR_DOMAIN_MEMORY_SOURCE_NONE + && dst->mem.source == VIR_DOMAIN_MEMORY_SOURCE_FILE) || + (src->mem.source == VIR_DOMAIN_MEMORY_SOURCE_FILE + && dst->mem.source == VIR_DOMAIN_MEMORY_SOURCE_NONE))) { + + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, + _("Target memoryBacking source '%1$s' doesn't match source memoryBacking source'%2$s'"),

+ virDomainMemorySourceTypeToString(dst->mem.source), + virDomainMemorySourceTypeToString(src->mem.source)); + return false; + } } for (i = 0; i < src->nmems; i++) { -- 2.34.1