[PATCH 5/8] x86/boot: Drop xen_virt_end

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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 52975142d154 ("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@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

This effectively reverts d0ae97d4136e ("x86-64: properly handle alias mappings
beyond _end"), because the preconditions for the change are no longer valid.
---
 xen/arch/x86/livepatch.c          | 3 ++-
 xen/arch/x86/mm.c                 | 3 ++-
 xen/arch/x86/setup.c              | 6 ------
 xen/include/asm-x86/x86_64/page.h | 2 --
 4 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/xen/arch/x86/livepatch.c b/xen/arch/x86/livepatch.c
index 49f0d902e5bb..d056b1ed8b41 100644
--- a/xen/arch/x86/livepatch.c
+++ b/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);
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 9bd4e5cc1d2f..fdc548a9cb4a 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -786,7 +786,8 @@ bool is_iomem_page(mfn_t mfn)
 static int update_xen_mappings(unsigned long mfn, unsigned int cacheattr)
 {
     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);
 
     /*
      * Something is catastrophically broken if someone is trying to change the
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 6613e56a2184..0e0e706404a3 100644
--- a/xen/arch/x86/setup.c
+++ b/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
diff --git a/xen/include/asm-x86/x86_64/page.h 
b/xen/include/asm-x86/x86_64/page.h
index f9faf7f38348..cb1db107c424 100644
--- a/xen/include/asm-x86/x86_64/page.h
+++ b/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.
-- 
2.11.0