xen/acpi: Rework acpi_os_map_memory() and acpi_os_unmap_memory()

The functions acpi_os_{un,}map_memory() are meant to be arch-agnostic
while the __acpi_os_{un,}map_memory() are meant to be arch-specific.

Currently, the former are still containing x86 specific code.

To avoid this rather strange split, the generic helpers are reworked so
they are arch-agnostic. This requires the introduction of a new helper
__acpi_os_unmap_memory() that will undo any mapping done by
__acpi_os_map_memory().

Currently, the arch-helper for unmap is basically a no-op so it only
returns whether the mapping was arch specific. But this will change
in the future.

Note that the x86 version of acpi_os_map_memory() was already able to
able the 1MB region. Hence why there is no addition of new code.

Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Rahul Singh <rahul.singh@arm.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Rahul Singh <rahul.singh@arm.com>
Tested-by: Elliott Mitchell <ehem+xen@m5p.com>

xen/arch/arm/acpi/lib.c

@@ -30,6 +30,10 @@ char *__acpi_map_table(paddr_t phys, unsigned long size)
     unsigned long base, offset, mapped_size;
     int idx;
 
+    /* No arch specific implementation after early boot */
+    if ( system_state >= SYS_STATE_boot )
+        return NULL;
+
     offset = phys & (PAGE_SIZE - 1);
     mapped_size = PAGE_SIZE - offset;
     set_fixmap(FIXMAP_ACPI_BEGIN, maddr_to_mfn(phys), PAGE_HYPERVISOR);
@@ -49,6 +53,14 @@ char *__acpi_map_table(paddr_t phys, unsigned long size)
     return ((char *) base + offset);
 }
 
+bool __acpi_unmap_table(const void *ptr, unsigned long size)
+{
+    vaddr_t vaddr = (vaddr_t)ptr;
+
+    return ((vaddr >= FIXMAP_ADDR(FIXMAP_ACPI_BEGIN)) &&
+            (vaddr < (FIXMAP_ADDR(FIXMAP_ACPI_END) + PAGE_SIZE)));
+}
+
 /* True to indicate PSCI 0.2+ is implemented */
 bool __init acpi_psci_present(void)
 {

xen/arch/x86/acpi/lib.c

@@ -46,6 +46,10 @@ char *__acpi_map_table(paddr_t phys, unsigned long size)
 	if ((phys + size) <= (1 * 1024 * 1024))
 		return __va(phys);
 
+	/* No further arch specific implementation after early boot */
+	if (system_state >= SYS_STATE_boot)
+		return NULL;
+
 	offset = phys & (PAGE_SIZE - 1);
 	mapped_size = PAGE_SIZE - offset;
 	set_fixmap(FIX_ACPI_END, phys);
@@ -66,6 +70,20 @@ char *__acpi_map_table(paddr_t phys, unsigned long size)
 	return ((char *) base + offset);
 }
 
+bool __acpi_unmap_table(const void *ptr, unsigned long size)
+{
+	unsigned long vaddr = (unsigned long)ptr;
+
+	if ((vaddr >= DIRECTMAP_VIRT_START) &&
+	    (vaddr < DIRECTMAP_VIRT_END)) {
+		ASSERT(!((__pa(ptr) + size - 1) >> 20));
+		return true;
+	}
+
+	return ((vaddr >= __fix_to_virt(FIX_ACPI_END)) &&
+		(vaddr < (__fix_to_virt(FIX_ACPI_BEGIN) + PAGE_SIZE)));
+}
+
 unsigned int acpi_get_processor_id(unsigned int cpu)
 {
 	unsigned int acpiid, apicid;

xen/drivers/acpi/osl.c

@@ -92,27 +92,29 @@ acpi_physical_address __init acpi_os_get_root_pointer(void)
 void __iomem *
 acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 {
-	if (system_state >= SYS_STATE_boot) {
-		mfn_t mfn = _mfn(PFN_DOWN(phys));
-		unsigned int offs = phys & (PAGE_SIZE - 1);
+	void *ptr;
+	mfn_t mfn = _mfn(PFN_DOWN(phys));
+	unsigned int offs = PAGE_OFFSET(phys);
 
-		/* The low first Mb is always mapped on x86. */
-		if (IS_ENABLED(CONFIG_X86) && !((phys + size - 1) >> 20))
-			return __va(phys);
-		return __vmap(&mfn, PFN_UP(offs + size), 1, 1,
-			      ACPI_MAP_MEM_ATTR, VMAP_DEFAULT) + offs;
-	}
-	return __acpi_map_table(phys, size);
+	/* Try the arch specific implementation first */
+	ptr = __acpi_map_table(phys, size);
+	if (ptr)
+		return ptr;
+
+	/* No common implementation for early boot map */
+	if (unlikely(system_state < SYS_STATE_boot))
+		return NULL;
+
+	ptr = __vmap(&mfn, PFN_UP(offs + size), 1, 1,
+		     ACPI_MAP_MEM_ATTR, VMAP_DEFAULT);
+
+	return !ptr ? NULL : (ptr + offs);
 }
 
 void acpi_os_unmap_memory(void __iomem * virt, acpi_size size)
 {
-	if (IS_ENABLED(CONFIG_X86) &&
-	    (unsigned long)virt >= DIRECTMAP_VIRT_START &&
-	    (unsigned long)virt < DIRECTMAP_VIRT_END) {
-		ASSERT(!((__pa(virt) + size - 1) >> 20));
+	if (__acpi_unmap_table(virt, size))
 		return;
-	}
 
 	if (system_state >= SYS_STATE_boot)
 		vunmap((void *)((unsigned long)virt & PAGE_MASK));

xen/include/xen/acpi.h

@@ -68,6 +68,7 @@ typedef int (*acpi_table_entry_handler) (struct acpi_subtable_header *header, co
 
 unsigned int acpi_get_processor_id (unsigned int cpu);
 char * __acpi_map_table (paddr_t phys_addr, unsigned long size);
+bool __acpi_unmap_table(const void *ptr, unsigned long size);
 int acpi_boot_init (void);
 int acpi_boot_table_init (void);
 int acpi_numa_init (void);