drivers/char: support up to 1M BAR0 of xhci

AMD's XHCI has BAR0 of 1M (compared to 64K on Intel). Map it as a whole
(reserving more space in the fixmap). Make fixmap slot conditional on
CONFIG_XHCI.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/include/asm/fixmap.h

@@ -25,7 +25,7 @@
 #include <asm/msi.h>
 #include <acpi/apei.h>
 
-#define MAX_XHCI_PAGES 16
+#define MAX_XHCI_PAGES 256
 
 /*
  * Here we define all the compile-time 'special' virtual
@@ -45,8 +45,10 @@ enum fixed_addresses {
     FIX_COM_BEGIN,
     FIX_COM_END,
     FIX_EHCI_DBGP,
+#ifdef CONFIG_XHCI
     FIX_XHCI_BEGIN,
     FIX_XHCI_END = FIX_XHCI_BEGIN + MAX_XHCI_PAGES - 1,
+#endif
 #ifdef CONFIG_XEN_GUEST
     FIX_PV_CONSOLE,
     FIX_XEN_SHARED_INFO,

xen/drivers/char/xhci-dbc.c

@@ -268,10 +268,12 @@ static void *dbc_sys_map_xhc(uint64_t phys, size_t size)
 {
     size_t i;
 
-    if ( size != MAX_XHCI_PAGES * PAGE_SIZE )
+    if ( size > MAX_XHCI_PAGES * PAGE_SIZE )
         return NULL;
 
-    for ( i = FIX_XHCI_END; i >= FIX_XHCI_BEGIN; i-- )
+    size >>= PAGE_SHIFT;
+
+    for ( i = FIX_XHCI_END; i > FIX_XHCI_END - size; i-- )
     {
         set_fixmap_nocache(i, phys);
         phys += PAGE_SIZE;