[libvirt][PATCH RESEND v10 1/5] qemu: provide support to query the SGX capability

[Michal Prívozník]

On 2/23/22 04:41, Huang, Haibin wrote:
> I accept all comments. But I didn't your point for this comment .
>>> +static void
>>> +virQEMUCapsFormatSGXInfo(virQEMUCaps *qemuCaps, virBuffer *buf) {
>>> +    virSGXCapabilityPtr sgx =
>>> +virQEMUCapsGetSGXCapabilities(qemuCaps);
>>> +
>>> +    virBufferAddLit(buf, "<sgx>\n");
>>> +    virBufferAdjustIndent(buf, 2);
>>> +    virBufferAsprintf(buf, "<flc>%s</flc>\n", sgx->flc ? "yes" :
>>> + "no");
>>
>> ... which is in contradiction with the way we format it.
> [Haibin] sorry, I don't get your point, can you give me the details
> 
> Does you mean that change virBufferAsprintf(buf, "<flc>%s</flc>\n", sgx->flc ? "yes" : "no"); to virBufferAsprintf(buf, "<flc>%u</flc>\n", sgx->flc);

No. You can keep this particual virBufferAsprintf() as is. What I have
problem with is the parsing side. So if this virQEMUCapsFormatSGXInfo()
function is called, if produces the following XML:

  <sgx>
    <flc>no</flc>
    <epc_size>1024</epc_size>
  </sgx>

(I've made the values up)

This corresponds to: sgx->flc = false; sgx->epc_size = 1024;

But when the XML is parsed, in virQEMUCapsParseSGXInfo(), it would se
the following values:

sgx->flc = true; sgx->epc_size = 2014;

Notice the change in ->flc? This is because
virXPathBoolean("boolean(./sgx/flc)") does not evaluate the value of
<flc/> element, but only whether the xpath exists. Therefore, even if
flc's element value is "no", it does exist and as such is evaluated to true.

Hope this cleans things up.

Michal