Re: [XEN PATCH v2] xen: introduce kconfig options to disable hypercalls

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Fri, 27 Dec 2024, Jan Beulich wrote:
> On 19.12.2024 10:29, Sergiy Kibrik wrote:
> > --- a/xen/arch/x86/Makefile
> > +++ b/xen/arch/x86/Makefile
> > @@ -74,12 +74,12 @@ obj-y += hpet.o
> >  obj-y += vm_event.o
> >  obj-y += xstate.o
> >  
> > -ifneq ($(CONFIG_PV_SHIM_EXCLUSIVE),y)
> > -obj-y += domctl.o
> > +obj-$(CONFIG_DOMCTL) += domctl.o
> > +ifeq ($(CONFIG_PLATFORM_OP),y)
> >  obj-y += platform_hypercall.o
> >  obj-$(CONFIG_COMPAT) += x86_64/platform_hypercall.o
> > -obj-y += sysctl.o
> >  endif
> 
> Personally I'd prefer if we avoided ifeq here:
> 
> obj-$(CONFIG_PLATFORM_OP) += platform_hypercall.o
> obj-$(filter $(CONFIG_COMPAT),$(CONFIG_PLATFORM_OP)) += 
> x86_64/platform_hypercall.o
> 
> Yet I realize this (once again) may be contentious.
> 
> > --- a/xen/common/Kconfig
> > +++ b/xen/common/Kconfig
> > @@ -516,4 +516,33 @@ config TRACEBUFFER
> >       to be collected at run time for debugging or performance analysis.
> >       Memory and execution overhead when not active is minimal.
> >  
> > +menu "Supported hypercall interfaces"
> > +   visible if DOM0LESS_BOOT && EXPERT
> > +
> > +config SYSCTL
> > +   bool "Enable sysctl hypercall"
> > +   depends on !PV_SHIM_EXCLUSIVE
> > +   default y
> > +
> > +config DOMCTL
> > +   bool "Enable domctl hypercalls"
> > +   depends on !PV_SHIM_EXCLUSIVE
> > +   default y
> > +
> > +config HVM_OP
> > +   bool "Enable HVM hypercalls"
> > +   depends on HVM
> > +   default y
> > +
> > +config PLATFORM_OP
> > +   bool "Enable platform hypercalls"
> > +   depends on !PV_SHIM_EXCLUSIVE
> > +   default y
> 
> Just to re-iterate an earlier comment: Andrew (imo validly) raised concern of
> such negative dependencies. As said before, imo we'd better resolve that 
> before
> extending the issue (whether by the patch I once sent or something else is 
> then
> secondary).

How would you express the !PV_SHIM_EXCLUSIVE dependency without using
negative dependencies?


> > --- a/xen/common/Makefile
> > +++ b/xen/common/Makefile
> > @@ -66,10 +66,10 @@ obj-bin-$(CONFIG_X86) += $(foreach n,decompress bunzip2 
> > unxz unlzma lzo unlzo un
> >  obj-$(CONFIG_COMPAT) += $(addprefix compat/,domain.o memory.o multicall.o 
> > xlat.o)
> >  
> >  ifneq ($(CONFIG_PV_SHIM_EXCLUSIVE),y)
> > -obj-y += domctl.o
> >  obj-y += monitor.o
> > -obj-y += sysctl.o
> >  endif
> > +obj-$(CONFIG_DOMCTL) += domctl.o
> > +obj-$(CONFIG_SYSCTL) += sysctl.o
> 
> These two then want to move back up into their normal slots.
> 
> Jan
>