[Xen-devel] [PATCH v3 2/2] x86/setup: remap Xen image up to PFN_DOWN(__pa(_end))

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

Current limit, PFN_DOWN(xen_phys_start), introduced by commit b280442
(x86: make Xen early boot code relocatable) is not reliable. Potentially
its value may fall below PFN_DOWN(__pa(_end)) and then part of Xen image
may not be mapped after relocation. This will not happen in current code
thanks to "x86/setup: do not relocate over current Xen image placement"
patch. Though this safety measure may save a lot of debugging time when
somebody decide to relax existing relocation restrictions one day.
Additionally, remapping will execute a bit faster due to this change.

Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
---
 xen/arch/x86/setup.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 9f8abd9..ac163e2 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -973,6 +973,11 @@ void __init noreturn __start_xen(unsigned long mbi_p)
             l3_pgentry_t *pl3e;
             l2_pgentry_t *pl2e;
             int i, j, k;
+            /*
+             * We have to calculate xen_remap_end_pfn before
+             * xen_phys_start change.
+             */
+            unsigned long xen_remap_end_pfn = PFN_DOWN(__pa(_end));
 
             /* Select relocation address. */
             e = end - reloc_size;
@@ -1002,7 +1007,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
                     /* Not present, 1GB mapping, or already relocated? */
                     if ( !(l3e_get_flags(*pl3e) & _PAGE_PRESENT) ||
                          (l3e_get_flags(*pl3e) & _PAGE_PSE) ||
-                         (l3e_get_pfn(*pl3e) > PFN_DOWN(xen_phys_start)) )
+                         (l3e_get_pfn(*pl3e) > xen_remap_end_pfn) )
                         continue;
                     *pl3e = l3e_from_intpte(l3e_get_intpte(*pl3e) +
                                             xen_phys_start);
@@ -1012,7 +1017,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
                         /* Not present, PSE, or already relocated? */
                         if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) ||
                              (l2e_get_flags(*pl2e) & _PAGE_PSE) ||
-                             (l2e_get_pfn(*pl2e) > PFN_DOWN(xen_phys_start)) )
+                             (l2e_get_pfn(*pl2e) > xen_remap_end_pfn) )
                             continue;
                         *pl2e = l2e_from_intpte(l2e_get_intpte(*pl2e) +
                                                 xen_phys_start);
@@ -1036,7 +1041,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
                 unsigned int flags;
 
                 if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) ||
-                     (l2e_get_pfn(*pl2e) > PFN_DOWN(xen_phys_start)) )
+                     (l2e_get_pfn(*pl2e) > xen_remap_end_pfn) )
                     continue;
 
                 if ( !using_2M_mapping() )
-- 
1.7.10.4


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