With boot-time switching between paging modes, XEN_PV and XEN_PVH can be
boot into 4-level paging mode.

Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Cc: Juergen Gross <jgr...@suse.com>
---
 arch/x86/kernel/head_64.S | 12 ++++++------
 arch/x86/xen/Kconfig      |  5 -----
 arch/x86/xen/mmu_pv.c     | 21 +++++++++++++++++++++
 3 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index ebdcb08a91cb..9de244aa72fd 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -37,12 +37,12 @@
  *
  */
 
+#define l4_index(x)    (((x) >> 39) & 511)
 #define pud_index(x)   (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
 
-#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
-PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE48)
-PGD_START_KERNEL = pgd_index(__START_KERNEL_map)
-#endif
+L4_PAGE_OFFSET = l4_index(__PAGE_OFFSET_BASE48)
+L4_START_KERNEL = l4_index(__START_KERNEL_map)
+
 L3_START_KERNEL = pud_index(__START_KERNEL_map)
 
        .text
@@ -363,9 +363,9 @@ NEXT_PAGE(early_dynamic_pgts)
 #if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
 NEXT_PAGE(init_top_pgt)
        .quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
-       .org    init_top_pgt + PGD_PAGE_OFFSET*8, 0
+       .org    init_top_pgt + L4_PAGE_OFFSET*8, 0
        .quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
-       .org    init_top_pgt + PGD_START_KERNEL*8, 0
+       .org    init_top_pgt + L4_START_KERNEL*8, 0
        /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
        .quad   level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
 
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index 1ecd419811a2..027987638e98 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -17,9 +17,6 @@ config XEN_PV
        bool "Xen PV guest support"
        default y
        depends on XEN
-       # XEN_PV is not ready to work with 5-level paging.
-       # Changes to hypervisor are also required.
-       depends on !X86_5LEVEL
        select XEN_HAVE_PVMMU
        select XEN_HAVE_VPMU
        help
@@ -78,6 +75,4 @@ config XEN_DEBUG_FS
 config XEN_PVH
        bool "Support for running as a PVH guest"
        depends on XEN && XEN_PVHVM && ACPI
-       # Pre-built page tables are not ready to handle 5-level paging.
-       depends on !X86_5LEVEL
        def_bool n
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index bc5fddd64217..55b529c36f16 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -558,6 +558,22 @@ static void xen_set_p4d(p4d_t *ptr, p4d_t val)
 
        xen_mc_issue(PARAVIRT_LAZY_MMU);
 }
+
+#if CONFIG_PGTABLE_LEVELS >= 5
+__visible p4dval_t xen_p4d_val(p4d_t p4d)
+{
+       return pte_mfn_to_pfn(p4d.p4d);
+}
+PV_CALLEE_SAVE_REGS_THUNK(xen_p4d_val);
+
+__visible p4d_t xen_make_p4d(p4dval_t p4d)
+{
+       p4d = pte_pfn_to_mfn(p4d);
+
+       return native_make_p4d(p4d);
+}
+PV_CALLEE_SAVE_REGS_THUNK(xen_make_p4d);
+#endif  /* CONFIG_PGTABLE_LEVELS >= 5 */
 #endif /* CONFIG_X86_64 */
 
 static int xen_pmd_walk(struct mm_struct *mm, pmd_t *pmd,
@@ -2430,6 +2446,11 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = 
{
 
        .alloc_pud = xen_alloc_pmd_init,
        .release_pud = xen_release_pmd_init,
+
+#if CONFIG_PGTABLE_LEVELS >= 5
+       .p4d_val = PV_CALLEE_SAVE(xen_p4d_val),
+       .make_p4d = PV_CALLEE_SAVE(xen_make_p4d),
+#endif
 #endif /* CONFIG_X86_64 */
 
        .activate_mm = xen_activate_mm,
-- 
2.13.2

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