[tip:x86/mm] x86/xen: Allow XEN_PV and XEN_PVH to be enabled with X86_5LEVEL

From: tip-bot for Kirill A. Shutemov
Date: Wed Feb 21 2018 - 06:01:44 EST


Commit-ID: b9952ec78778aa7ae5b8df672668aece6fc93d2a
Gitweb: https://git.kernel.org/tip/b9952ec78778aa7ae5b8df672668aece6fc93d2a
Author: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
AuthorDate: Fri, 16 Feb 2018 14:49:46 +0300
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 21 Feb 2018 10:19:18 +0100

x86/xen: Allow XEN_PV and XEN_PVH to be enabled with X86_5LEVEL

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

Tested-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Link: http://lkml.kernel.org/r/20180216114948.68868-2-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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 145d7b9..3e9de0f 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -38,12 +38,12 @@
*
*/

+#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_BASE_L4)
-PGD_START_KERNEL = pgd_index(__START_KERNEL_map)
-#endif
+L4_PAGE_OFFSET = l4_index(__PAGE_OFFSET_BASE_L4)
+L4_START_KERNEL = l4_index(__START_KERNEL_map)
+
L3_START_KERNEL = pud_index(__START_KERNEL_map)

.text
@@ -386,9 +386,9 @@ NEXT_PAGE(early_dynamic_pgts)
#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
NEXT_PGD_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
.fill PTI_USER_PGD_FILL,8,0
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index f605825..c1f98f3 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -18,9 +18,6 @@ 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
@@ -79,6 +76,4 @@ 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 d850762..3f4fec5 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -538,6 +538,22 @@ 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,
@@ -2411,6 +2427,11 @@ 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,