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<p class="MsoNormal"><span style="font-size:11.0pt">On 6/1/22, 11:37 PM, "Michal Prívozník" <mprivozn@redhat.com> wrote:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> Worst case scenario we can do a version check. It's very suboptimal<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> because if somebody backports your patches in QEMU, libvirt will stop<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> working despite having the version check.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> Therefore, I'm more inclined to just use the newest API and well, 6.2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> won't work. In the long run - it's just one release that has the feature<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> but libvirt can't use it versus plenty of releases (that come after 7.0)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> which have the feature and libvirt can use it. If we go this way then<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> we'll still need version check, but the other way round:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> if (qemuCaps->version < 7000000)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> virQEMUCapsClear(qemuCaps, QEMU_CAPS_SGX_EPC);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> Or just exit early and don't even bother detecting SGX when version is<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> not 7.0.0:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> if (qemuCaps->version < 7000000)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> return 0;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> This has the downside that when somebody backports QEMU patches to 6.2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> to match the QAPI of 7.0 libvirt would still refuse to use the feature.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> But one can argue that at that point the maintainer should also patch<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> libvirt (very trivial patch to remove these two lines of condition).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> This is the reason we like QEMU to make features introspectable - we<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> could avoid all of this if we were able to detect .node attribute :-(<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> Now that I look at the output of query-qmp-schema command I see that 6.2<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> returns:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "237",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "members": [<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "sgx",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "sgx1",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "sgx2",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "flc",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "section-size",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "int"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "meta-type": "object"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> while 7.0 returns:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "237",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "members": [<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "sgx",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "sgx1",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "sgx2",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "flc",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "bool"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "section-size",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "int",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "features": [<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "deprecated"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> ]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> },<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "name": "sections",<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "type": "[454]"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> ],<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> "meta-type": "object"<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> So maybe in the end libvirt CAN know the difference without having to do<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> any version check. We have a "dialect" of XPATH that we use to traverse<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">> the QMP schema: look at the comment above virQEMUQAPISchemaPathGet().<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">This is awesome! Thank you so much for this very informative explanation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">QEMU 7.0.0 provides more NUMA info in SGX part, so if we see "sections" in<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">QAPI schema, we can assume .node attribute is required.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Let me try this solution at first. We can support both QEMU 6.2.0 and 7.0.0 in<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">V13 patches if it is doable.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Lin.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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