xen: set max_pfn_mapped to the last pfn mapped

Do not set max_pfn_mapped to the end of the initial memory mappings,
that also contain pages that don't belong in pfn space (like the mfn
list).

Set max_pfn_mapped to the last real pfn mapped in the initial memory
mappings that is the pfn backing _end.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
LKML-Reference: <alpine.DEB.2.00.1103171739050.3382@kaball-desktop>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index a2d78ad35a55..6e27979506c1 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1701,9 +1701,6 @@ static __init void xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
                 for (pteidx = 0; pteidx < PTRS_PER_PTE; pteidx++, pfn++) {
                         pte_t pte;
 
-                        if (pfn > max_pfn_mapped)
-                                max_pfn_mapped = pfn;
-
                         if (!pte_none(pte_page[pteidx]))
                                 continue;
 
@@ -1761,6 +1758,12 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
         pud_t *l3;
         pmd_t *l2;
 
+        /* max_pfn_mapped is the last pfn mapped in the initial memory
+         * mappings. Considering that on Xen after the kernel mappings we
+         * have the mappings of some pages that don't exist in pfn space, we
+         * set max_pfn_mapped to the last real pfn mapped. */
+        max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->mfn_list));
+
         /* Zap identity mapping */
         init_level4_pgt[0] = __pgd(0);
 
@@ -1865,9 +1868,7 @@ __init pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd,
         initial_kernel_pmd =
                 extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
 
-        max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->pt_base) +
-                                  xen_start_info->nr_pt_frames * PAGE_SIZE +
-                                  512*1024);
+        max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->mfn_list));
 
         kernel_pmd = m2v(pgd[KERNEL_PGD_BOUNDARY].pgd);
         memcpy(initial_kernel_pmd, kernel_pmd, sizeof(pmd_t) * PTRS_PER_PMD);