RE: [PATCH v2 24/26] xen/domctl: wrap arch-specific domctl-op with CONFIG_MGMT_HYPERCALLS

["Penny, Zheng" <penny.zheng@xxxxxxx>]

[Public]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Monday, October 13, 2025 4:30 PM
> To: Penny, Zheng <penny.zheng@xxxxxxx>
> Cc: Huang, Ray <Ray.Huang@xxxxxxx>; Andrew Cooper
> <andrew.cooper3@xxxxxxxxxx>; Anthony PERARD <anthony.perard@xxxxxxxxxx>;
> Orzel, Michal <Michal.Orzel@xxxxxxx>; Julien Grall <julien@xxxxxxx>; Roger Pau
> Monné <roger.pau@xxxxxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>;
> Bertrand Marquis <bertrand.marquis@xxxxxxx>; Volodymyr Babchuk
> <Volodymyr_Babchuk@xxxxxxxx>; Tamas K Lengyel <tamas@xxxxxxxxxxxxx>;
> Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2 24/26] xen/domctl: wrap arch-specific domctl-op with
> CONFIG_MGMT_HYPERCALLS
>
> On 13.10.2025 09:18, Penny, Zheng wrote:
> >> -----Original Message-----
> >> From: Jan Beulich <jbeulich@xxxxxxxx>
> >> Sent: Monday, October 13, 2025 2:41 PM
> >>
> >> On 11.10.2025 08:44, Penny, Zheng wrote:
> >>>> -----Original Message-----
> >>>> From: Jan Beulich <jbeulich@xxxxxxxx>
> >>>> Sent: Thursday, September 11, 2025 9:03 PM
> >>>>
> >>>>> --- a/xen/lib/x86/Makefile
> >>>>> +++ b/xen/lib/x86/Makefile
> >>>>> @@ -1,3 +1,3 @@
> >>>>>  obj-y += cpuid.o
> >>>>>  obj-y += msr.o
> >>>>> -obj-y += policy.o
> >>>>> +obj-$(CONFIG_MGMT_HYPERCALLS) += policy.o
> >>>>
> >>>> Fair parts of cpuid.c also become unreachable. And all of msr.c afaics.
> >>>>
> >>>
> >>> I just found that the functions defined here, as helpers/libraries,
> >>> are used in
> >> tools/libs/guest/xg_cpuid_x86.c too. Emmm, to make compiler happy, I
> >> still need to provide stubs for them when MGMT_HYPERCALLS=n. Or any
> better suggestion?
> >>
> >> How does the Makefile change here affect tools/libs/guest/? What
> >> would you need stubs for there?
> >>
> >
> > Like Function xc_cpu_policy_is_compatible() in 
> > tools/libs/guest/xg_cpuid_x86.c
> is also using x86_cpu_policies_are_compatible() to do the comparison between
> host and guest. If making xen/lib/x86/plocy.o guarded by MGMT_HYPERCALLS,
> we will have "undefined reference " error. Imo, it is not suitable to guard 
> files
> tools/libs/guest/xg_cpuid_x86.o with MGMT_HYPERCALLS.
>
> Correct, but I still don't see what you're getting at. This Makefile is used 
> in the
> hypervisor build only. In tools/libs/guest/Makefile.common we have
>
> ifeq ($(CONFIG_X86),y) # Add libx86 to the build vpath %.c 
> ../../../xen/lib/x86
>
> OBJS-y                 += cpuid.o msr.o policy.o
> endif
>

Oh, true...
They are separately compiled with different Makefile.
It is fair parts of cpuid.c(x86_cpuid_copy_to{,from}_buffer) which got 
"undefined reference". Lets omit this part of change.

> Jan