Re: [PATCH REBASE 7/7] qemu: Use memory-backend-* for regular guest memory

On Tue, Sep 15, 2020 at 11:53:56AM +0200, Igor Mammedov wrote: > On Tue, 15 Sep 2020 10:54:46 +0200 > Michal Privoznik <mprivozn(a)redhat.com&gt; wrote: > >> On 9/8/20 3:55 PM, Ján Tomko wrote: >>> On a Tuesday in 2020, Michal Privoznik wrote: >> >>>> diff --git >>>> a/tests/qemuxml2argvdata/memfd-memory-default-hugepage.x86_64-latest.args >>>> b/tests/qemuxml2argvdata/memfd-memory-default-hugepage.x86_64-latest.args >>>> index 5d256c42bc..b43e7d9c3c 100644 >>>> --- >>>> a/tests/qemuxml2argvdata/memfd-memory-default-hugepage.x86_64-latest.args >>>> +++ >>>> b/tests/qemuxml2argvdata/memfd-memory-default-hugepage.x86_64-latest.args >>>> @@ -12,14 +12,16 @@ QEMU_AUDIO_DRV=none \ >>>> -S \ >>>> -object 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,\ >>>> +memory-backend=pc.ram \ >>>> -cpu qemu64 \ >>>> -m 14336 \ >>>> --mem-prealloc \ >>>> +-object memory-backend-memfd,id=pc.ram,hugetlb=yes,hugetlbsize=2097152,\ >>>> +share=yes,prealloc=yes,size=15032385536 \ >>>> -overcommit mem-lock=off \ >>>> -smp 8,sockets=1,dies=1,cores=8,threads=1 \ >>>> -object >>>> memory-backend-memfd,id=ram-node0,hugetlb=yes,hugetlbsize=2097152,\ >>>> -share=yes,size=15032385536,host-nodes=3,policy=preferred \ >>>> +share=yes,prealloc=yes,size=15032385536,host-nodes=3,policy=preferred \ >>>> -numa node,nodeid=0,cpus=0-7,memdev=ram-node0 \ >>>> -uuid 126f2720-6f8e-45ab-a886-ec9277079a67 \ >>>> -display none \ >>> >>> Should we format all the fields twice in these cases? >> >> Ah, good question. Honestly, I don't remember, it was slightly longer >> ago that I've written these patches. Igor, do you perhaps remember >> whether libvirt needs to specify both: -machine memory-backend=$id and >> -object memory-backend-*,id=$id? > > the later defines backend and the former uses it, > short answer is yes. > > you do not need > --mem-prealloc > if you explicitly set "prealloc=yes" on backend. > > I'd prefer if libvirt stopped using old -mem-prealloc and -mem-path > in favor of explicit properties on backend, so QEMU could deprecate > it and drop aliasing code which uses global properties hack. IIRC, we tried todo that in the past and the change to use a backend impacted migration ABI compatibility.