Re: [PATCH 5/7] qmp: Add the qmp_query_sgx_capabilities()

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 9/9/21 2:06 PM, Yang Zhong wrote:
> On Thu, Sep 09, 2021 at 11:36:58AM +0200, Philippe Mathieu-Daudé wrote:
>> On 9/9/21 4:51 AM, Yang Zhong wrote:
>>> On Wed, Sep 08, 2021 at 10:38:59AM +0200, Philippe Mathieu-Daudé wrote:
>>>> On 9/8/21 10:19 AM, Yang Zhong wrote:
>>>>> Libvirt can use qmp_query_sgx_capabilities() to get the host
>>>>> sgx capabilities.
>>>>>
>>>>> Signed-off-by: Yang Zhong <yang.zhong@intel.com>
>>>>> ---
>>>>>  hw/i386/sgx.c              | 66 ++++++++++++++++++++++++++++++++++++++
>>>>>  include/hw/i386/sgx.h      |  1 +
>>>>>  qapi/misc-target.json      | 18 +++++++++++
>>>>>  target/i386/monitor.c      |  5 +++
>>>>>  tests/qtest/qmp-cmd-test.c |  1 +
>>>>>  5 files changed, 91 insertions(+)
>>>>
>>>>> +SGXInfo *sgx_get_capabilities(Error **errp)
>>>>> +{
>>>>> +    SGXInfo *info = NULL;
>>>>> +    uint32_t eax, ebx, ecx, edx;
>>>>> +
>>>>> +    int fd = qemu_open_old("/dev/sgx_vepc", O_RDWR);
>>>>> +    if (fd < 0) {
>>>>> +        error_setg(errp, "SGX is not enabled in KVM");
>>>>> +        return NULL;
>>>>> +    }
>>>>
>>>> Is this Linux specific?
>>>
>>>   Philippe, The /dev/sgx_vepc node is used for KVM side to expose the SGX
>>>   EPC section to guest. Libvirt then use the '-machine none' qemu command 
>>>   to query host SGX capabilities(especially for host SGX EPC section size)
>>>   to decide how many SGX VMs will be started in server. If this node doesn't
>>>   exist, the reason is host can't support SGX or SGX KVM module is not compiled
>>>   in the kernel. thanks!
>>
>> Sorry but you didn't answer my question in an obvious way... Yes or no?
> 
>   Yes, this is Linux specific. thanks!

You made me have a deeper look at the code. So SGX (Kconfig) requires
KVM, which is only supported on Linux host. Thus this Linux specific
code is only built on Linux host. Thanks.