path: root/arch/arm64/include/asm/stage2_pgtable-nopud.h
diff options
authorSuzuki K Poulose <>2016-03-23 12:22:33 +0000
committerChristoffer Dall <>2016-04-21 14:58:21 +0200
commitda04fa04dc91e7dae79629f28804391cbcf6e604 (patch)
treee735ceb3c024a703f9dcb746d2e30d4920b4acff /arch/arm64/include/asm/stage2_pgtable-nopud.h
parent8684e701df5a3f52e3ff580128cbd5d71fcd5f5c (diff)
kvm: arm64: Get rid of fake page table levels
On arm64, the hardware supports concatenation of upto 16 tables, at entry level for stage2 translations and we make use that whenever possible. This could lead to reduced number of translation levels than the normal (stage1 table) table. Also, since the IPA(40bit) is smaller than the some of the supported VA_BITS (e.g, 48bit), there could be different number of levels in stage-1 vs stage-2 tables. To reuse the kernel host page table walker for stage2 we have been using a fake software page table level, not known to the hardware. But with 16K translations, there could be upto 2 fake software levels (with 48bit VA and 40bit IPA), which complicates the code. Hence, we want to get rid of the hack. Now that we have explicit accessors for hyp vs stage2 page tables, define the stage2 walker helpers accordingly based on the actual table used by the hardware. Once we know the number of translation levels used by the hardware, it is merely a job of defining the helpers based on whether a particular level is folded or not, looking at the number of levels. Some facts before we calculate the translation levels: 1) Smallest page size supported by arm64 is 4K. 2) The minimum number of bits resolved at any page table level is (PAGE_SHIFT - 3) at intermediate levels. Both of them implies, minimum number of bits required for a level change is 9. Since we can concatenate upto 16 tables at stage2 entry, the total number of page table levels used by the hardware for resolving N bits is same as that for (N - 4) bits (with concatenation), as there cannot be a level in between (N, N-4) as per the above rules. Hence, we have STAGE2_PGTABLE_LEVELS = PGTABLE_LEVELS(KVM_PHYS_SHIFT - 4) With the current IPA limit (40bit), for all supported translations and VA_BITS, we have the following condition (even for 36bit VA with 16K page size): CONFIG_PGTABLE_LEVELS >= STAGE2_PGTABLE_LEVELS. So, for e.g, if PUD is present in stage2, it is present in the hyp(host). Hence, we fall back to the host definition if we find that a level is not folded. Otherwise we redefine it accordingly. A build time check is added to make sure the above condition holds. If this condition breaks in future, we can rearrange the host level helpers and fix our code easily. Cc: Marc Zyngier <> Cc: Christoffer Dall <> Reviewed-by: Christoffer Dall <> Signed-off-by: Suzuki K Poulose <>
Diffstat (limited to 'arch/arm64/include/asm/stage2_pgtable-nopud.h')
1 files changed, 39 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/stage2_pgtable-nopud.h b/arch/arm64/include/asm/stage2_pgtable-nopud.h
new file mode 100644
index 000000000000..5ee87b54ebf3
--- /dev/null
+++ b/arch/arm64/include/asm/stage2_pgtable-nopud.h
@@ -0,0 +1,39 @@
+ * Copyright (C) 2016 - ARM Ltd
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <>.
+ */
+#ifndef __ARM64_S2_PGTABLE_NOPUD_H_
+#define __ARM64_S2_PGTABLE_NOPUD_H_
+#define S2_PTRS_PER_PUD 1
+#define S2_PUD_SIZE (_AC(1, UL) << S2_PUD_SHIFT)
+#define S2_PUD_MASK (~(S2_PUD_SIZE-1))
+#define stage2_pgd_none(pgd) (0)
+#define stage2_pgd_present(pgd) (1)
+#define stage2_pgd_clear(pgd) do { } while (0)
+#define stage2_pgd_populate(pgd, pud) do { } while (0)
+#define stage2_pud_offset(pgd, address) ((pud_t *)(pgd))
+#define stage2_pud_free(x) do { } while (0)
+#define stage2_pud_addr_end(addr, end) (end)
+#define stage2_pud_table_empty(pmdp) (0)