[PATCH] qemu: Don't use memory-backend-memfd for NVDIMMs

[Daniel Henrique Barboza]

On 6/22/21 4:11 AM, Michal Privoznik wrote:
> If guest is configured to use memfd then the function that build
> memory-backend-* part of command line will put
> memory-backend-memfd, always. Even for NVDIMMs. This is not
> correct, because NVDIMMs need a backing path (usually to a real
> host NVDIMM device). Therefore, regardless of memfd being
> requested, we have to stick with memory-backend-file.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---


Reviewed-by: Daniel Henrique Barboza <danielhb413 at gmail.com>

>   src/qemu/qemu_command.c                               |  3 ++-
>   .../memfd-memory-numa.x86_64-latest.args              |  6 ++++--
>   tests/qemuxml2argvdata/memfd-memory-numa.xml          | 11 +++++++++++
>   tests/qemuxml2xmltest.c                               |  3 ++-
>   4 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index ea513693f7..0473e7deaa 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -3052,7 +3052,8 @@ qemuBuildMemoryBackendProps(virJSONValue **backendProps,
>   
>       props = virJSONValueNewObject();
>   
> -    if (def->mem.source == VIR_DOMAIN_MEMORY_SOURCE_MEMFD) {
> +    if (!mem->nvdimmPath &&
> +        def->mem.source == VIR_DOMAIN_MEMORY_SOURCE_MEMFD) {
>           backendType = "memory-backend-memfd";
>   
>           if (useHugepage) {
> diff --git a/tests/qemuxml2argvdata/memfd-memory-numa.x86_64-latest.args b/tests/qemuxml2argvdata/memfd-memory-numa.x86_64-latest.args
> index 5e54908666..3b33db3c55 100644
> --- a/tests/qemuxml2argvdata/memfd-memory-numa.x86_64-latest.args
> +++ b/tests/qemuxml2argvdata/memfd-memory-numa.x86_64-latest.args
> @@ -10,13 +10,15 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-instance-00000092/.config \
>   -name guest=instance-00000092,debug-threads=on \
>   -S \
>   -object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/tmp/lib/domain--1-instance-00000092/master-key.aes"}' \
> --machine pc-i440fx-2.3,accel=kvm,usb=off,dump-guest-core=off \
> +-machine pc-i440fx-2.3,accel=kvm,usb=off,dump-guest-core=off,nvdimm=on \
>   -cpu qemu64 \
> --m 14336 \
> +-m size=14680064k,slots=16,maxmem=1099511627776k \
>   -overcommit mem-lock=off \
>   -smp 8,sockets=1,dies=1,cores=8,threads=1 \
>   -object '{"qom-type":"memory-backend-memfd","id":"ram-node0","hugetlb":true,"hugetlbsize":2097152,"share":true,"prealloc":true,"size":15032385536,"host-nodes":[3],"policy":"preferred"}' \
>   -numa node,nodeid=0,cpus=0-7,memdev=ram-node0 \
> +-object '{"qom-type":"memory-backend-file","id":"memnvdimm0","mem-path":"/tmp/nvdimm","share":true,"prealloc":true,"size":536870912,"host-nodes":[3],"policy":"preferred"}' \
> +-device nvdimm,node=0,memdev=memnvdimm0,id=nvdimm0,slot=0 \
>   -uuid 126f2720-6f8e-45ab-a886-ec9277079a67 \
>   -display none \
>   -no-user-config \
> diff --git a/tests/qemuxml2argvdata/memfd-memory-numa.xml b/tests/qemuxml2argvdata/memfd-memory-numa.xml
> index 3f448790a6..d9e1a9f564 100644
> --- a/tests/qemuxml2argvdata/memfd-memory-numa.xml
> +++ b/tests/qemuxml2argvdata/memfd-memory-numa.xml
> @@ -1,6 +1,7 @@
>   <domain type='kvm'>
>     <name>instance-00000092</name>
>     <uuid>126f2720-6f8e-45ab-a886-ec9277079a67</uuid>
> +  <maxMemory slots='16' unit='KiB'>1099511627776</maxMemory>
>     <memory unit='KiB'>14680064</memory>
>     <currentMemory unit='KiB'>14680064</currentMemory>
>     <memoryBacking>
> @@ -41,5 +42,15 @@
>       <memballoon model='virtio'>
>         <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
>       </memballoon>
> +    <memory model='nvdimm'>
> +      <source>
> +        <path>/tmp/nvdimm</path>
> +      </source>
> +      <target>
> +        <size unit='KiB'>523264</size>
> +        <node>0</node>
> +      </target>
> +      <address type='dimm' slot='0'/>
> +    </memory>
>     </devices>
>   </domain>
> diff --git a/tests/qemuxml2xmltest.c b/tests/qemuxml2xmltest.c
> index 40e027aaa4..c5005d41a0 100644
> --- a/tests/qemuxml2xmltest.c
> +++ b/tests/qemuxml2xmltest.c
> @@ -1305,7 +1305,8 @@ mymain(void)
>       DO_TEST("memfd-memory-numa",
>               QEMU_CAPS_OBJECT_MEMORY_MEMFD,
>               QEMU_CAPS_OBJECT_MEMORY_MEMFD_HUGETLB,
> -            QEMU_CAPS_OBJECT_MEMORY_FILE);
> +            QEMU_CAPS_OBJECT_MEMORY_FILE,
> +            QEMU_CAPS_DEVICE_NVDIMM);
>       DO_TEST("memfd-memory-default-hugepage",
>               QEMU_CAPS_OBJECT_MEMORY_MEMFD,
>               QEMU_CAPS_OBJECT_MEMORY_MEMFD_HUGETLB,
>