[Xen-devel] [PATCH] xen: partially revert "xen: set max_pfn_mapped to the last pfn mapped"

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

We only need to set max_pfn_mapped to the last pfn mapped on x86_64 to
make sure that cleanup_highmap doesn't remove important mappings at
_end.

We don't need to do this on x86_32 because cleanup_highmap is not called
on x86_32. Besides lowering max_pfn_mapped on x86_32 has the unwanted
side effect of limiting the amount of memory available for the 1:1
kernel pagetable allocation.

This patch reverts the x86_32 part of the original patch.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index dc708dc..afe1d54 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1599,6 +1599,11 @@ static void __init xen_map_identity_early(pmd_t *pmd, 
unsigned long max_pfn)
                for (pteidx = 0; pteidx < PTRS_PER_PTE; pteidx++, pfn++) {
                        pte_t pte;
 
+#ifdef CONFIG_X86_32
+                       if (pfn > max_pfn_mapped)
+                               max_pfn_mapped = pfn;
+#endif
+
                        if (!pte_none(pte_page[pteidx]))
                                continue;
 
@@ -1766,7 +1771,9 @@ pgd_t * __init 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->mfn_list));
+       max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->pt_base) +
+                                 xen_start_info->nr_pt_frames * PAGE_SIZE +
+                                 512*1024);
 
        kernel_pmd = m2v(pgd[KERNEL_PGD_BOUNDARY].pgd);
        memcpy(initial_kernel_pmd, kernel_pmd, sizeof(pmd_t) * PTRS_PER_PMD);

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