[Xen-devel] [PATCH 3/7] xen/mmu: Release the Xen provided L4 (PGD) back.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

Since we are not using it and somebody else could use it.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 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 a59070b..48bdc9f 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1782,20 +1782,21 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, 
unsigned long max_pfn)
        /* Unpin Xen-provided one */
        pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
 
-       /* Switch over */
-       pgd = init_level4_pgt;
-
        /*
         * At this stage there can be no user pgd, and no page
         * structure to attach it to, so make sure we just set kernel
         * pgd.
         */
        xen_mc_batch();
-       __xen_write_cr3(true, __pa(pgd));
+       __xen_write_cr3(true, __pa(init_level4_pgt));
        xen_mc_issue(PARAVIRT_LAZY_CPU);
 
-       memblock_reserve(__pa(xen_start_info->pt_base),
-                        xen_start_info->nr_pt_frames * PAGE_SIZE);
+       /* Offset by one page since the original pgd is going bye bye */
+       memblock_reserve(__pa(xen_start_info->pt_base + PAGE_SIZE),
+                        (xen_start_info->nr_pt_frames * PAGE_SIZE) - 
PAGE_SIZE);
+       /* and also RW it so it can actually be used. */
+       set_page_prot(pgd, PAGE_KERNEL);
+       clear_page(pgd);
 }
 #else  /* !CONFIG_X86_64 */
 static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
-- 
1.7.7.6


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