Re: [PATCH v14 11/15] conf: Introduce SGX EPC element into device memory xml

On Wed, Jul 27, 2022 at 12:34:57 +0200, Michal Privoznik wrote: > From: Lin Yang <lin.a.yang(a)intel.com&gt; > > With NUMA config: > > <devices> > ... > <memory model='sgx-epc'> > <source> > <nodemask>0-1</nodemask> > </source> > <target> > <size unit='KiB'>512</size> > <node>0</node> > </target> > </memory> > ... > </devices> > > Without NUMA config: > > <devices> > ... > <memory model='sgx-epc'> > <target> > <size unit='KiB'>512</size> > </target> > </memory> > ... > </devices> > > Signed-off-by: Lin Yang <lin.a.yang(a)intel.com&gt; > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > --- [...] > diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst > index 1ed969ac3e..bdd0fcea8e 100644 > --- a/docs/formatdomain.rst > +++ b/docs/formatdomain.rst > @@ -7940,6 +7940,20 @@ Example: usage of the memory devices > <current unit='KiB'>524288</current> > </target> > </memory> > + <memory model='sgx-epc'> > + <source> > + <nodemask>0-1</nodemask> > + </source> > + <target> > + <size unit='KiB'>16384</size> > + <node>0</node> > + </target> > + </memory> > + <memory model='sgx-epc'> > + <target> > + <size unit='KiB'>16384</size> > + </target> > + </memory> > </devices> > ... > > @@ -7948,7 +7962,9 @@ Example: usage of the memory devices > 1.2.14` Provide ``nvdimm`` model that adds a Non-Volatile DIMM module. > :since:`Since 3.2.0` Provide ``virtio-pmem`` model to add a paravirtualized > persistent memory device. :since:`Since 7.1.0` Provide ``virtio-mem`` model > - to add paravirtualized memory device. :since:`Since 7.9.0` > + to add paravirtualized memory device. :since:`Since 7.9.0` Provide > + ``sgx-epc`` model to add a SGX enclave page cache (EPC) memory to the guest. > + :since:`Since 8.7.0 and QEMU 6.2.0` I don't quite understand from this description whether this is real memory usable by the guest OS or something for internal use by the hypervisor. Specifically which leads me to questioning this is that the example sizes are very tiny compared to real memory sizing.

Additionally in qemuDomainDefValidateMemoryHotplug you are changing the code to specifically exclude the sizing of the 'sgx-epc' memory devices from the total size of the memory, but this contrasts with the memory _not_ being excluded from the initial memory calculation in virDomainDefGetMemoryInitial which is used to format the initial memory argument ('-m size=...'). Thus at least one of them is wrong. If this is not guest usable memory, then the <memory> element should not be used to bolt this on, but rather add a new element similarly to what we have when AMD SEV is in use.