[libvirt][PATCH v11 1/4] qemu: provide support to query the SGX capability

[Peter Krempa]

On Thu, May 12, 2022 at 01:21:45 +0000, Huang, Haibin wrote:
> 
> > -----Original Message-----
> > From: Peter Krempa <pkrempa at redhat.com>
> > Sent: Thursday, May 12, 2022 12:05 AM
> > To: Yang, Lin A <lin.a.yang at intel.com>
> > Cc: libvir-list at redhat.com; Huang, Haibin <haibin.huang at intel.com>; Ding,
> > Jian-feng <jian-feng.ding at intel.com>; Zhong, Yang <yang.zhong at intel.com>
> > Subject: Re: [libvirt][PATCH v11 1/4] qemu: provide support to query the SGX
> > capability
> > 
> > On Tue, May 10, 2022 at 23:11:09 -0700, Lin Yang wrote:
> > > From: Haibin Huang <haibin.huang at intel.com>
> > >
> > > QEMU version >= 6.2.0 provides support for creating enclave on SGX x86
> > > platform using Software Guard Extensions (SGX) feature.
> > > This patch adds support to query the SGX capability from the qemu.
> > >
> > > Signed-off-by: Haibin Huang <haibin.huang at intel.com>
> > > ---
> > >  src/conf/domain_capabilities.c                |  10 ++
> > >  src/conf/domain_capabilities.h                |  13 ++
> > >  src/libvirt_private.syms                      |   1 +
> > >  src/qemu/qemu_capabilities.c                  | 119 ++++++++++++++++++
> > >  src/qemu/qemu_capabilities.h                  |   6 +
> > >  src/qemu/qemu_capspriv.h                      |   4 +
> > >  src/qemu/qemu_monitor.c                       |  10 ++
> > >  src/qemu/qemu_monitor.h                       |   3 +
> > >  src/qemu/qemu_monitor_json.c                  | 104 +++++++++++++--
> > >  src/qemu/qemu_monitor_json.h                  |   9 ++
> > >  .../caps_6.2.0.x86_64.replies                 |  22 +++-
> > >  .../caps_6.2.0.x86_64.xml                     |   5 +
> > >  .../caps_7.0.0.x86_64.replies                 |  22 +++-
> > >  .../caps_7.0.0.x86_64.xml                     |   5 +
> > >  14 files changed, 318 insertions(+), 15 deletions(-)
> > 
> > This is not a full review. Couple of points:
> > 
> > 1) Do not mix other changes with adding QEMU_CAPS* stuff
> >     Basically theres waaay too much going on in this patch and it
> >     definitely can be separated into smaller chunks. The QEMU_CAPS is
> >     just one of them.
> >     Separate at least:
> >         - qemu monitor command introduction
> >         - domain capabilities data structs for sgx
> >         - parsing and formatting of the XML
> >         - adding of the QEMU_CAPS_ flag
> > 2) caps for qemu-7.1 were added very recently
> >     You'll need to fix that one too since you added an extra query. Make
> >     sure that you _don't_ add the faking of SXG into that file, but
> >     rather the error case. My box doesn't support SGX so it will be
> >     overwritten in my next refresh anyways.
> > 
> > [...]
> > 
> > > @@ -4706,6 +4805,21 @@ virQEMUCapsFormatSEVInfo(virQEMUCaps
> > *qemuCaps,
> > > virBuffer *buf)  }
> > >
> > >
> > > +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");
> > 
> > Don't use the ternary operator ('?'), use a full if/else branch instead or pick a
> > better data structure.
> > 
> [Haibin]   do you mean change to like below?
>    if (sgx->flc) {
>         virBufferAsprintf(buf, "<flc>%s</flc>\n", "yes");
>     } else {
>         virBufferAsprintf(buf, "<flc>%s</flc>\n", "no");
>     }

Yes. Alternatively you can use a temporary variable and fill that via an
'if' statement.

Finally you can use a virTristateBool variable type to hold the 'flc'
value and use our internal convertors for it.