x86/boot: Drop xen_virt_end

The calculation in __start_xen() for xen_virt_end is an opencoding of
ROUNDUP(_end, 2M).  This is __2M_rwdata_end as provided by the linker script.

This corrects the bound calculations in arch_livepatch_init() and
update_xen_mappings() to not enforce 2M alignment when Xen is not compiled
with CONFIG_XEN_ALIGN_2M.

Furthermore, since 52975142d1 ("x86/boot: Create the l2_xenmap[] mappings
dynamically"), there have not been extraneous mappings to delete, meaning that
the call to destroy_xen_mappings() has been a no-op.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/livepatch.c

@@ -17,6 +17,7 @@
 #include <asm/fixmap.h>
 #include <asm/nmi.h>
 #include <asm/livepatch.h>
+#include <asm/setup.h>
 
 static bool has_active_waitqueue(const struct vm_event_domain *ved)
 {
@@ -343,7 +344,7 @@ void __init arch_livepatch_init(void)
 {
     void *start, *end;
 
-    start = (void *)xen_virt_end;
+    start = (void *)__2M_rwdata_end;
     end = (void *)(XEN_VIRT_END - FIXADDR_X_SIZE - NR_CPUS * PAGE_SIZE);
 
     BUG_ON(end <= start);

xen/arch/x86/mm.c

@@ -787,7 +787,8 @@ static int update_xen_mappings(unsigned long mfn, unsigned int cacheattr)
 {
     int err = 0;
     bool alias = mfn >= PFN_DOWN(xen_phys_start) &&
-         mfn < PFN_UP(xen_phys_start + xen_virt_end - XEN_VIRT_START);
+                 mfn <  PFN_UP(xen_phys_start + (unsigned long)__2M_rwdata_end -
+                               XEN_VIRT_START);
     unsigned long xen_va =
         XEN_VIRT_START + ((mfn - PFN_DOWN(xen_phys_start)) << PAGE_SHIFT);
 

xen/arch/x86/setup.c

@@ -136,8 +136,6 @@ cpumask_t __read_mostly cpu_present_map;
 
 unsigned long __read_mostly xen_phys_start;
 
-unsigned long __read_mostly xen_virt_end;
-
 char __section(".bss.stack_aligned") __aligned(STACK_SIZE)
     cpu0_stack[STACK_SIZE];
 
@@ -1573,10 +1571,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     }
 #endif
 
-    xen_virt_end = ((unsigned long)_end + (1UL << L2_PAGETABLE_SHIFT) - 1) &
-                   ~((1UL << L2_PAGETABLE_SHIFT) - 1);
-    destroy_xen_mappings(xen_virt_end, XEN_VIRT_START + BOOTSTRAP_MAP_BASE);
-
     /*
      * If not using 2M mappings to gain suitable pagetable permissions
      * directly from the relocation above, remap the code/data

xen/include/asm-x86/x86_64/page.h

@@ -23,8 +23,6 @@ static inline unsigned long canonicalise_addr(unsigned long addr)
 
 #include <xen/pdx.h>
 
-extern unsigned long xen_virt_end;
-
 /*
  * Note: These are solely for the use by page_{get,set}_owner(), and
  *       therefore don't need to handle the XEN_VIRT_{START,END} range.