[Xen-devel] [PATCH 2/2] xen: set max_pfn_mapped to the last pfn mapped

[stefano.stabellini@xxxxxxxxxxxxx]

From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
---
 arch/x86/xen/mmu.c |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 5e92b61..6092f73 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1653,9 +1653,6 @@ 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;
 
@@ -1713,6 +1710,12 @@ __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);
 
@@ -1817,9 +1820,7 @@ __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);
-- 
1.5.6.5


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