I understand and thank you very much for your meticulous explanation.
-----Original Message----- From: Michal Prívozník <mprivozn@redhat.com> Sent: Wednesday, February 23, 2022 8:16 PM To: Huang, Haibin <haibin.huang@intel.com>; libvir-list@redhat.com; berrange@redhat.com; Ding, Jian-feng <jian-feng.ding@intel.com>; Yang, Lin A <lin.a.yang@intel.com>; Lu, Lianhao <lianhao.lu@intel.com> Subject: Re: [libvirt][PATCH RESEND v10 1/5] qemu: provide support to query the SGX capability
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