x86,arm: Change arch_livepatch_quiesce() declaration.

On ARM we need an alternative VA region to poke in the
hypervisor .text data. And since this is setup during runtime
we may fail (it uses vmap so most likely error is ENOMEM).

As such this error needs to be bubbled up and also abort
the livepatching if it occurs.

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/arch/arm/livepatch.c

@@ -7,8 +7,9 @@
 #include <xen/livepatch_elf.h>
 #include <xen/livepatch.h>
 
-void arch_livepatch_quiesce(void)
+int arch_livepatch_quiesce(void)
 {
+    return -ENOSYS;
 }
 
 void arch_livepatch_revive(void)

xen/arch/x86/livepatch.c

@@ -15,10 +15,12 @@
 
 #define PATCH_INSN_SIZE 5
 
-void arch_livepatch_quiesce(void)
+int arch_livepatch_quiesce(void)
 {
     /* Disable WP to allow changes to read-only pages. */
     write_cr0(read_cr0() & ~X86_CR0_WP);
+
+    return 0;
 }
 
 void arch_livepatch_revive(void)

xen/common/livepatch.c

@@ -1004,11 +1004,17 @@ static int livepatch_list(xen_sysctl_livepatch_list_t *list)
 static int apply_payload(struct payload *data)
 {
     unsigned int i;
+    int rc;
 
     printk(XENLOG_INFO LIVEPATCH "%s: Applying %u functions\n",
             data->name, data->nfuncs);
 
-    arch_livepatch_quiesce();
+    rc = arch_livepatch_quiesce();
+    if ( rc )
+    {
+        printk(XENLOG_ERR LIVEPATCH "%s: unable to quiesce!\n", data->name);
+        return rc;
+    }
 
     for ( i = 0; i < data->nfuncs; i++ )
         arch_livepatch_apply_jmp(&data->funcs[i]);
@@ -1028,10 +1034,16 @@ static int apply_payload(struct payload *data)
 static int revert_payload(struct payload *data)
 {
     unsigned int i;
+    int rc;
 
     printk(XENLOG_INFO LIVEPATCH "%s: Reverting\n", data->name);
 
-    arch_livepatch_quiesce();
+    rc = arch_livepatch_quiesce();
+    if ( rc )
+    {
+        printk(XENLOG_ERR LIVEPATCH "%s: unable to quiesce!\n", data->name);
+        return rc;
+    }
 
     for ( i = 0; i < data->nfuncs; i++ )
         arch_livepatch_revert_jmp(&data->funcs[i]);

xen/include/xen/livepatch.h

@@ -71,7 +71,7 @@ int arch_livepatch_verify_func(const struct livepatch_func *func);
  * These functions are called around the critical region patching live code,
  * for an architecture to take make appropratie global state adjustments.
  */
-void arch_livepatch_quiesce(void);
+int arch_livepatch_quiesce(void);
 void arch_livepatch_revive(void);
 
 void arch_livepatch_apply_jmp(struct livepatch_func *func);