[libvirt][PATCH RESEND v12 6/6] qemu: Add command-line to generate SGX EPC memory backend

[Yang, Lin A]

On 5/30/22, 6:09 AM, "Michal Prívozník" <mprivozn at redhat.com> wrote:

> On 5/18/22 09:59, Haibin Huang wrote:
> > From: Lin Yang <lin.a.yang at intel.com>
> >
> > According to the result parsing from xml, add the argument of
> > SGX EPC memory backend into QEMU command line:
> >
> >     #qemu-system-x86_64 \
> >         ...... \
> >         -object memory-backend-epc,id=memepc0,size=64M,prealloc=on \
> >         -object memory-backend-epc,id=memepc1,size=28M \
> >         -machine sgx-epc.0.memdev=memepc0,sgx-epc.1.memdev=memepc1
> >
> > Signed-off-by: Lin Yang <lin.a.yang at intel.com>
> > Signed-off-by: Haibin Huang <haibin.huang at intel.com>
> > ---
> >  src/qemu/qemu_alias.c                         |  3 +-
> >  src/qemu/qemu_command.c                       | 53 +++++++++++++++++--
> >  .../sgx-epc.x86_64-6.2.0.args                 | 37 +++++++++++++
> >  tests/qemuxml2argvtest.c                      |  2 +
> >  4 files changed, 90 insertions(+), 5 deletions(-)
> >  create mode 100644 tests/qemuxml2argvdata/sgx-epc.x86_64-6.2.0.args
> >
> > diff --git a/src/qemu/qemu_alias.c b/src/qemu/qemu_alias.c
> > index e5a946cbed..03c79bcf0e 100644
> > --- a/src/qemu/qemu_alias.c
> > +++ b/src/qemu/qemu_alias.c
> > @@ -467,7 +467,8 @@ qemuDeviceMemoryGetAliasID(virDomainDef *def,
> >       * valid */
> >      if (!oldAlias &&
> >          mem->model != VIR_DOMAIN_MEMORY_MODEL_VIRTIO_PMEM &&
> > -        mem->model != VIR_DOMAIN_MEMORY_MODEL_VIRTIO_MEM)
> > +        mem->model != VIR_DOMAIN_MEMORY_MODEL_VIRTIO_MEM &&
> > +        mem->model != VIR_DOMAIN_MEMORY_MODEL_SGX_EPC)
> >          return mem->info.addr.dimm.slot;
> >
> >      for (i = 0; i < def->nmems; i++) {
> > diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> > index 4807b137b6..9c83f0e168 100644
> > --- a/src/qemu/qemu_command.c
> > +++ b/src/qemu/qemu_command.c
> > @@ -3774,6 +3774,10 @@ qemuBuildMemoryBackendProps(virJSONValue **backendProps,
> >          if (systemMemory)
> >              disableCanonicalPath = true;
> >
> > +    } else if (mem->model == VIR_DOMAIN_MEMORY_MODEL_SGX_EPC) {
> > +        backendType = "memory-backend-epc";
> > +        if (!priv->memPrealloc)
> > +            prealloc = true;
> >      } else if (useHugepage || mem->nvdimmPath || memAccess ||
> >          def->mem.source == VIR_DOMAIN_MEMORY_SOURCE_FILE) {
> >
> > @@ -3934,6 +3938,11 @@ qemuBuildMemoryBackendProps(virJSONValue **backendProps,
> >                             _("this qemu doesn't support the "
> >                               "memory-backend-memfd object"));
> >              return -1;
> > +        } else if (STREQ(backendType, "memory-backend-epc") &&
> > +                   !virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_SGX_EPC)) {
> > +            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> > +                           _("this qemu doesn't support the memory-backend-epc object"));
> > +            return -1;
> >          }
> >
> >          rc = 0;
> > @@ -6979,6 +6988,7 @@ qemuBuildMachineCommandLine(virCommand *cmd,
> >      virCPUDef *cpu = def->cpu;
> >      g_auto(virBuffer) buf = VIR_BUFFER_INITIALIZER;
> >      size_t i;
> > +    int epcNum = 0;
> >
> >      virCommandAddArg(cmd, "-machine");
> >      virBufferAdd(&buf, def->os.machine, -1);
> > @@ -7199,6 +7209,25 @@ qemuBuildMachineCommandLine(virCommand *cmd,
> >          virBufferAddLit(&buf, ",graphics=off");
> >      }
> >
> > +    /* add sgx epc memory to -machine parameter */
> > +    for (i = 0; i < def->nmems; i++) {
> > +        switch ((virDomainMemoryModel) def->mems[i]->model) {
> > +        case VIR_DOMAIN_MEMORY_MODEL_SGX_EPC:
> > +            virBufferAsprintf(&buf, ",sgx-epc.%d.memdev=mem%s", epcNum++,
> > +                              def->mems[i]->info.alias);
>
> So there really isn't any better way to specify sgx-epc than through -M?
> This way libvirt loses capability to set th device @id attribute which
> means we have to jump through hoops (like in your patch 2/6) when the
> @id value is expected.
>
> I vaguely pointing this out earlier (but maybe I just thought about
> pointing it out and never did - it's been a while since I've reviewed
> these patches), but I don't know what the consensus was.

I was not involved in the QEMU SGX patches review process and don’t
know the reason why it use -machine instead of -device. The initial
patch introduce separate QEMU argument -sgx-epc, but finally was
updated to -machine according to the comments.

https://lists.nongnu.org/archive/html/qemu-devel/2021-05/msg00644.html

Thanks,
Lin.
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