Make MEM_ACCESS configurable

Select MEM_ACCESS_ALWAYS_ON on x86 to mark that MEM_ACCESS is not
configurable on x86. Avoid selecting it on ARM.
Rename HAS_MEM_ACCESS to MEM_ACCESS everywhere. Add a prompt and a
description to MEM_ACCESS in xen/common/Kconfig.

The result is that the user-visible option is MEM_ACCESS, and it is
configurable only on ARM (disabled by default). At the moment the
arch-specific mem_access code remains enabled on ARM, even with
MEM_ACCESS=y.

The purpose is to reduce code size. The option doesn't depend on EXPERT
because it would be nice to ecurity-support configurations without
MEM_ACCESS and a non-expert should be able to disable it.

Suggested-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <julien.grall@arm.com>

CC: dgdegra@tycho.nsa.gov
CC: andrew.cooper3@citrix.com
CC: George.Dunlap@eu.citrix.com
CC: ian.jackson@eu.citrix.com
CC: jbeulich@suse.com
CC: julien.grall@arm.com
CC: konrad.wilk@oracle.com
CC: sstabellini@kernel.org
CC: tim@xen.org
CC: wei.liu2@citrix.com

---
Changes in v5:
- change MEM_ACCESS_ALWAYS_ON to bool
- change default for MEM_ACCESS, default y if MEM_ACCESS_ALWAYS_ON

Changes in v4:
- remove HAS_MEM_ACCESS
- move MEM_ACCESS_ALWAYS_ON to common
- combile default and bool to def_bool

Changes in v3:
- keep HAS_MEM_ACCESS to mark that an arch can do MEM_ACCESS
- introduce MEM_ACCESS_ALWAYS_ON
- the main MEM_ACCESS option is in xen/common/Kconfig

Changes in v2:
- patch added

tools/firmware/xen-dir/shim.config

@@ -29,7 +29,7 @@ CONFIG_COMPAT=y
 CONFIG_CORE_PARKING=y
 CONFIG_HAS_ALTERNATIVE=y
 CONFIG_HAS_EX_TABLE=y
-CONFIG_HAS_MEM_ACCESS=y
+CONFIG_MEM_ACCESS=y
 CONFIG_HAS_MEM_PAGING=y
 CONFIG_HAS_MEM_SHARING=y
 CONFIG_HAS_PDX=y

xen/arch/arm/Kconfig

@@ -17,7 +17,6 @@ config ARM
 	def_bool y
 	select HAS_ALTERNATIVE
 	select HAS_DEVICE_TREE
-	select HAS_MEM_ACCESS
 	select HAS_PASSTHROUGH
 	select HAS_PDX
 

xen/arch/x86/Kconfig

@@ -15,7 +15,7 @@ config X86
 	select HAS_GDBSX
 	select HAS_IOPORTS
 	select HAS_KEXEC
-	select HAS_MEM_ACCESS
+	select MEM_ACCESS_ALWAYS_ON
 	select HAS_MEM_PAGING
 	select HAS_MEM_SHARING
 	select HAS_NS16550

xen/common/Kconfig

@@ -20,9 +20,17 @@ config HAS_DEVICE_TREE
 config HAS_EX_TABLE
 	bool
 
-config HAS_MEM_ACCESS
+config MEM_ACCESS_ALWAYS_ON
 	bool
 
+config MEM_ACCESS
+	def_bool MEM_ACCESS_ALWAYS_ON
+	prompt "Memory Access and VM events" if !MEM_ACCESS_ALWAYS_ON
+	---help---
+
+	  Framework to configure memory access types for guests and receive
+	  related events in userspace.
+
 config HAS_MEM_PAGING
 	bool
 

xen/common/Makefile

@@ -22,7 +22,7 @@ obj-y += lib.o
 obj-$(CONFIG_NEEDS_LIST_SORT) += list_sort.o
 obj-$(CONFIG_LIVEPATCH) += livepatch.o livepatch_elf.o
 obj-y += lzo.o
-obj-$(CONFIG_HAS_MEM_ACCESS) += mem_access.o
+obj-$(CONFIG_MEM_ACCESS) += mem_access.o
 obj-y += memory.o
 obj-y += monitor.o
 obj-y += multicall.o

xen/common/domctl.c

@@ -1085,7 +1085,7 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
         copyback = 1;
         break;
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
     case XEN_DOMCTL_set_access_required:
         if ( unlikely(current->domain == d) ) /* no domain_pause() */
             ret = -EPERM;

xen/include/xen/mem_access.h

@@ -78,7 +78,7 @@ long p2m_set_mem_access_multi(struct domain *d,
  */
 int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access);
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
 int mem_access_memop(unsigned long cmd,
                      XEN_GUEST_HANDLE_PARAM(xen_mem_access_op_t) arg);
 #else
@@ -88,7 +88,7 @@ int mem_access_memop(unsigned long cmd,
 {
     return -ENOSYS;
 }
-#endif /* CONFIG_HAS_MEM_ACCESS */
+#endif /* CONFIG_MEM_ACCESS */
 
 #endif /* _XEN_MEM_ACCESS_H */
 

xen/include/xsm/dummy.h

@@ -584,7 +584,7 @@ static XSM_INLINE int xsm_vm_event_control(XSM_DEFAULT_ARG struct domain *d, int
     return xsm_default_action(action, current->domain, d);
 }
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
 static XSM_INLINE int xsm_mem_access(XSM_DEFAULT_ARG struct domain *d)
 {
     XSM_ASSERT_ACTION(XSM_DM_PRIV);

xen/include/xsm/xsm.h

@@ -143,7 +143,7 @@ struct xsm_operations {
 
     int (*vm_event_control) (struct domain *d, int mode, int op);
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
     int (*mem_access) (struct domain *d);
 #endif
 
@@ -582,7 +582,7 @@ static inline int xsm_vm_event_control (xsm_default_t def, struct domain *d, int
     return xsm_ops->vm_event_control(d, mode, op);
 }
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
 static inline int xsm_mem_access (xsm_default_t def, struct domain *d)
 {
     return xsm_ops->mem_access(d);

xen/xsm/dummy.c

@@ -127,7 +127,7 @@ void __init xsm_fixup_ops (struct xsm_operations *ops)
 
     set_to_dummy_if_null(ops, vm_event_control);
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
     set_to_dummy_if_null(ops, mem_access);
 #endif
 

xen/xsm/flask/hooks.c

@@ -1256,7 +1256,7 @@ static int flask_vm_event_control(struct domain *d, int mode, int op)
     return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__VM_EVENT);
 }
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
 static int flask_mem_access(struct domain *d)
 {
     return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__MEM_ACCESS);
@@ -1803,7 +1803,7 @@ static struct xsm_operations flask_ops = {
 
     .vm_event_control = flask_vm_event_control,
 
-#ifdef CONFIG_HAS_MEM_ACCESS
+#ifdef CONFIG_MEM_ACCESS
     .mem_access = flask_mem_access,
 #endif