[PATCH v4 13/20] kvm: arm64: Configure VTCR_EL2.SL0 per VM

Suzuki K Poulose
2018-07-18T09:06:57Z

VTCR_EL2 holds the following key stage2 translation table
parameters:
SL0 - Entry level in the page table lookup.
T0SZ - Denotes the size of the memory addressed by the table.

We have been using fixed values for the SL0 depending on the
page size as we have a fixed IPA size. But since we are about
to make it dynamic, we need to calculate the SL0 at runtime
per VM. This patch adds a helper to compute the value of SL0
for a VM based on the IPA size.

Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <cdall@arm.com>
Cc: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
Changes since v3:
- Update reference to latest ARM ARM.
- Update per-vm VTCR value of SL0.
- Add helpers to decode levels from SL0.
- Didn't pick up Reviewed-by tag from Eric, as there
are some new changes in this version
---
arch/arm64/include/asm/kvm_arm.h | 51 +++++++++++++++++++++++++++++++---------
arch/arm64/kvm/guest.c | 2 ++
2 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 66cf1df..abc7107 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -120,7 +120,6 @@
#define VTCR_EL2_IRGN0_WBWA TCR_IRGN0_WBWA
#define VTCR_EL2_SL0_SHIFT 6
#define VTCR_EL2_SL0_MASK (3 << VTCR_EL2_SL0_SHIFT)
-#define VTCR_EL2_SL0_LVL1 (1 << VTCR_EL2_SL0_SHIFT)
#define VTCR_EL2_T0SZ_MASK 0x3f
#define VTCR_EL2_VS_SHIFT 19
#define VTCR_EL2_VS_8BIT (0 << VTCR_EL2_VS_SHIFT)
@@ -147,29 +146,59 @@
/*
* Stage2 translation configuration:
* 64kB pages (TG0 = 1)
- * 2 level page tables (SL = 1)
*/
-#define VTCR_EL2_TGRAN_FLAGS (VTCR_EL2_TG0_64K | VTCR_EL2_SL0_LVL1)
-#define VTTBR_X_TGRAN_MAGIC 38
+#define VTCR_EL2_TGRAN VTCR_EL2_TG0_64K
+#define VTCR_EL2_TGRAN_SL0_BASE 3UL
+
#elif defined(CONFIG_ARM64_16K_PAGES)
/*
* Stage2 translation configuration:
* 16kB pages (TG0 = 2)
- * 2 level page tables (SL = 1)
*/
-#define VTCR_EL2_TGRAN_FLAGS (VTCR_EL2_TG0_16K | VTCR_EL2_SL0_LVL1)
-#define VTTBR_X_TGRAN_MAGIC 42
+#define VTCR_EL2_TGRAN VTCR_EL2_TG0_16K
+#define VTCR_EL2_TGRAN_SL0_BASE 3UL
#else /* 4K */
/*
* Stage2 translation configuration:
* 4kB pages (TG0 = 0)
- * 3 level page tables (SL = 1)
*/
-#define VTCR_EL2_TGRAN_FLAGS (VTCR_EL2_TG0_4K | VTCR_EL2_SL0_LVL1)
-#define VTTBR_X_TGRAN_MAGIC 37
+#define VTCR_EL2_TGRAN VTCR_EL2_TG0_4K
+#define VTCR_EL2_TGRAN_SL0_BASE 2UL
#endif

-#define VTCR_EL2_FLAGS (VTCR_EL2_COMMON_BITS | VTCR_EL2_TGRAN_FLAGS)
+#define VTCR_EL2_FLAGS (VTCR_EL2_COMMON_BITS | VTCR_EL2_TGRAN)
+/*
+ * VTCR_EL2:SL0 indicates the entry level for Stage2 translation.
+ * Interestingly, it depends on the page size.
+ * See D.10.2.121, VTCR_EL2, in ARM DDI 0487C.a
+ *
+ * -----------------------------------------
+ * | Entry level | 4K | 16K/64K |
+ * ------------------------------------------
+ * | Level: 0 | 2 | - |
+ * ------------------------------------------
+ * | Level: 1 | 1 | 2 |
+ * ------------------------------------------
+ * | Level: 2 | 0 | 1 |
+ * ------------------------------------------
+ * | Level: 3 | - | 0 |
+ * ------------------------------------------
+ *
+ * That table roughly translates to :
+ *
+ * SL0(PAGE_SIZE, Entry_level) = SL0_BASE(PAGE_SIZE) - Entry_Level
+ *
+ * Where SL0_BASE(4K) = 2 and SL0_BASE(16K) = 3, SL0_BASE(64K) = 3, provided
+ * we take care of ruling out the unsupported cases and
+ * Entry_Level = 4 - Number_of_levels.
+ *
+ */
+#define VTCR_EL2_LVLS_TO_SL0(levels) \
+ ((VTCR_EL2_TGRAN_SL0_BASE - (4 - (levels))) << VTCR_EL2_SL0_SHIFT)
+#define VTCR_EL2_SL0_TO_LVLS(sl0) \
+ ((sl0) + 4 - VTCR_EL2_TGRAN_SL0_BASE)
+#define VTCR_EL2_LVLS(vtcr) \
+ VTCR_EL2_SL0_TO_LVLS(((vtcr) & VTCR_EL2_SL0_MASK) >> VTCR_EL2_SL0_SHIFT)
/*
* ARM VMSAv8-64 defines an algorithm for finding the translation table
* descriptors in section D4.2.8 in ARM DDI 0487C.a.
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index d24ee23..f7e1ece 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -491,6 +491,8 @@ int kvm_arm_config_vm(struct kvm *kvm)
vtcr |= (kvm_get_vmid_bits() == 16) ?
VTCR_EL2_VS_16BIT :
VTCR_EL2_VS_8BIT;
+
+ vtcr |= VTCR_EL2_LVLS_TO_SL0(kvm_stage2_levels(kvm));
kvm->arch.vtcr = vtcr;
return 0;
}
--
2.7.4