On Tue, Oct 06, 2020 at 06:20 PM +0200, Marc Hartmayer <mhartmay@xxxxxxxxxxxxx> wrote:
> ...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@xxxxxxxxxxxxx>
> ---
> 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
>
Gentle ping :)
--
Kind regards / Beste Grüße
Marc Hartmayer
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Gregor Pillen
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294
