xen/sysctl: wrap around sysctl hypercall

Wrap sysctl hypercall def and sysctl.o with CONFIG_SYSCTL, and since
PV_SHIM_EXCLUSIVE needs sorting in the future, we move them out of
PV_SHIM_EXCLUSIVE condition at the same time.

We need to make SYSCTL with prompt back, add help info and set default
value as y. We shall at least provide "# CONFIG_SYSCTL is not set" in preset
configs for PV shim on x86. With that, all dependent option get covered and
could be deleted.

Signed-off-by: Stefano Stabellini <stefano.stabellini@amd.com>
Signed-off-by: Sergiy Kibrik <Sergiy_Kibrik@epam.com>
Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/configs/pvshim_defconfig

@@ -19,12 +19,9 @@ CONFIG_EXPERT=y
 # CONFIG_SCHED_CREDIT2 is not set
 # CONFIG_SCHED_RTDS is not set
 # CONFIG_SCHED_ARINC653 is not set
-# CONFIG_LIVEPATCH is not set
 # CONFIG_SUPPRESS_DUPLICATE_SYMBOL_WARNINGS is not set
-# CONFIG_TRACEBUFFER is not set
 # CONFIG_AMD_IOMMU is not set
 # CONFIG_INTEL_IOMMU is not set
 # CONFIG_DEBUG is not set
 # CONFIG_GDBSX is not set
-# CONFIG_PM_OP is not set
-# CONFIG_PM_STATS is not set
+# CONFIG_SYSCTL is not set

xen/common/Kconfig

@@ -616,7 +616,11 @@ menu "Supported hypercall interfaces"
 	visible if EXPERT
 
 config SYSCTL
-	def_bool y
+	bool "Enable sysctl hypercall"
+	default y
+	help
+	  This option shall only be disabled on some dom0less systems, or
+	  PV shim on x86, to reduce Xen footprint.
 
 endmenu
 

xen/common/Makefile

@@ -49,6 +49,7 @@ obj-y += spinlock.o
 obj-$(CONFIG_STACK_PROTECTOR) += stack-protector.o
 obj-y += stop_machine.o
 obj-y += symbols.o
+obj-$(CONFIG_SYSCTL) += sysctl.o
 obj-y += tasklet.o
 obj-y += time.o
 obj-y += timer.o
@@ -70,7 +71,6 @@ obj-$(CONFIG_COMPAT) += $(addprefix compat/,domain.o memory.o multicall.o xlat.o
 ifneq ($(CONFIG_PV_SHIM_EXCLUSIVE),y)
 obj-y += domctl.o
 obj-$(CONFIG_VM_EVENT) += monitor.o
-obj-y += sysctl.o
 endif
 
 extra-y := symbols-dummy.o

xen/include/hypercall-defs.c

@@ -194,8 +194,10 @@ kexec_op(unsigned long op, void *uarg)
 #ifdef CONFIG_IOREQ_SERVER
 dm_op(domid_t domid, unsigned int nr_bufs, xen_dm_op_buf_t *bufs)
 #endif
-#ifndef CONFIG_PV_SHIM_EXCLUSIVE
+#ifdef CONFIG_SYSCTL
 sysctl(xen_sysctl_t *u_sysctl)
+#endif
+#ifndef CONFIG_PV_SHIM_EXCLUSIVE
 domctl(xen_domctl_t *u_domctl)
 paging_domctl_cont(xen_domctl_t *u_domctl)
 platform_op(xen_platform_op_t *u_xenpf_op)
@@ -273,8 +275,10 @@ physdev_op                         compat   do       hvm      hvm      do_arm
 #ifdef CONFIG_HVM
 hvm_op                             do       do       do       do       do
 #endif
-#ifndef CONFIG_PV_SHIM_EXCLUSIVE
+#ifdef CONFIG_SYSCTL
 sysctl                             do       do       do       do       do
+#endif
+#ifndef CONFIG_PV_SHIM_EXCLUSIVE
 domctl                             do       do       do       do       do
 #endif
 #ifdef CONFIG_KEXEC