Re: [RFC] qemu: virtiofs can be used without NUMA nodes

...if a machine memory-backend using shared memory is configured for the guest. This is especially important for QEMU machine types that don't have NUMA but virtiofs support. An example snippet: <domain type='kvm'> <name>test</name> <memory unit='KiB'>2097152</memory> <memoryBacking> <access mode='shared'/> </memoryBacking> <devices> <filesystem type='mount' accessmode='passthrough'> <driver type='virtiofs'/> <source dir='/tmp/test'/> <target dir='coffee'/> </filesystem> ... </devices> ... </domain> and the corresponding QEMU command line: /usr/bin/qemu-system-s390x \ -machine s390-ccw-virtio-5.2,memory-backend=s390.ram \ -m 2048 \ -object memory-backend-file,id=s390.ram,mem-path=/var/lib/libvirt/qemu/ram/46-test/s390.ram,share=yes,size=2147483648 \ ... Signed-off-by: Marc Hartmayer <mhartmay(a)linux.ibm.com&gt; --- Note: There are still some TODOs left... e.g. adapt the virtiofs documentation of libvirt.

--- src/qemu/qemu_validate.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c index a212605579d2..077a85b30802 100644 --- a/src/qemu/qemu_validate.c +++ b/src/qemu/qemu_validate.c @@ -3470,14 +3470,21 @@ qemuValidateDomainDeviceDefGraphics(const virDomainGraphicsDef *graphics, static int -qemuValidateDomainDefVirtioFSSharedMemory(const virDomainDef *def) +qemuValidateDomainDefVirtioFSSharedMemory(const virDomainDef *def, + virQEMUCapsPtr qemuCaps) { + const char *defaultRAMId = virQEMUCapsGetMachineDefaultRAMid(qemuCaps, + def->virtType, + def->os.machine); size_t numa_nodes = virDomainNumaGetNodeCount(def->numa); size_t i; - if (numa_nodes == 0) { + if (numa_nodes == 0 && + !(defaultRAMId && def->mem.access == VIR_DOMAIN_MEMORY_ACCESS_SHARED)) { + /* TODO do we need further checks here (e.g. check whether + * memory backend is supported by the QEMU binary)? */