x86/ACPI: fix S3 wakeup vector mapping

Use of __acpi_map_table() here was at least close to an abuse already
before, but it will now consistently return NULL here. Drop the layering
violation and use set_fixmap() directly. Re-use of the ACPI fixmap area
is hopefully going to remain "fine" for the time being.

Add checks to acpi_enter_sleep(): The vector now needs to be contained
within a single page, but the ACPI spec requires 64-byte alignment of
FACS anyway. Also bail if no wakeup vector was determined in the first
place, in part as preparation for a subsequent relaxation change.

Fixes: 1c4aa69ca1 ("xen/acpi: Rework acpi_os_map_memory() and acpi_os_unmap_memory()")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

xen/arch/x86/acpi/boot.c

@@ -443,6 +443,11 @@ acpi_fadt_parse_sleep_info(struct acpi_table_fadt *fadt)
 			"FACS is shorter than ACPI spec allow: %#x",
 			facs->length);
 
+	if (facs_pa % 64)
+		printk(KERN_WARNING PREFIX
+			"FACS is not 64-byte aligned: %#lx",
+			facs_pa);
+
 	acpi_sinfo.wakeup_vector = facs_pa + 
 		offsetof(struct acpi_table_facs, firmware_waking_vector);
 	acpi_sinfo.vector_width = 32;

xen/arch/x86/acpi/power.c

@@ -174,17 +174,20 @@ static void acpi_sleep_prepare(u32 state)
     if ( state != ACPI_STATE_S3 )
         return;
 
-    wakeup_vector_va = __acpi_map_table(
-        acpi_sinfo.wakeup_vector, sizeof(uint64_t));
-
     /* TBoot will set resume vector itself (when it is safe to do so). */
     if ( tboot_in_measured_env() )
         return;
 
+    set_fixmap(FIX_ACPI_END, acpi_sinfo.wakeup_vector);
+    wakeup_vector_va = fix_to_virt(FIX_ACPI_END) +
+                       PAGE_OFFSET(acpi_sinfo.wakeup_vector);
+
     if ( acpi_sinfo.vector_width == 32 )
         *(uint32_t *)wakeup_vector_va = bootsym_phys(wakeup_start);
     else
         *(uint64_t *)wakeup_vector_va = bootsym_phys(wakeup_start);
+
+    clear_fixmap(FIX_ACPI_END);
 }
 
 static void acpi_sleep_post(u32 state) {}
@@ -331,6 +334,12 @@ static long enter_state_helper(void *data)
  */
 int acpi_enter_sleep(struct xenpf_enter_acpi_sleep *sleep)
 {
+    if ( sleep->sleep_state == ACPI_STATE_S3 &&
+         (!acpi_sinfo.wakeup_vector || !acpi_sinfo.vector_width ||
+          (PAGE_OFFSET(acpi_sinfo.wakeup_vector) >
+           PAGE_SIZE - acpi_sinfo.vector_width / 8)) )
+        return -EOPNOTSUPP;
+
     if ( sleep->flags & XENPF_ACPI_SLEEP_EXTENDED )
     {
         if ( !acpi_sinfo.sleep_control.address ||