[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>
---
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)? */
virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
- _("virtiofs requires one or more NUMA nodes"));
+ _("virtiofs requires shared memory"));
return -1;
}
@@ -3591,7 +3598,7 @@ qemuValidateDomainDeviceDefFS(virDomainFSDefPtr fs,
_("virtiofs does not support multidevs"));
return -1;
}
- if (qemuValidateDomainDefVirtioFSSharedMemory(def) < 0)
+ if (qemuValidateDomainDefVirtioFSSharedMemory(def, qemuCaps) < 0)
return -1;
break;
--
2.25.4