Booting 5.4 on LX2160A reveals that KVM is non-functional:
kvm: Limiting the IPA size due to kernel Virtual Address limit
kvm [1]: IPA Size Limit: 43bits
kvm [1]: IDMAP intersecting with HYP VA, unable to continue
kvm [1]: error initializing Hyp mode: -22
Debugging shows:
kvm [1]: IDMAP page: 81a26000
kvm [1]: HYP VA range: 0:22ffffffff
as RAM is located at:
80000000-fbdfffff : System RAM
2080000000-237fffffff : System RAM
Comparing this with the same kernel on Armada 8040 shows:
kvm: Limiting the IPA size due to kernel Virtual Address limit
kvm [1]: IPA Size Limit: 43bits
kvm [1]: IDMAP page: 2a26000
kvm [1]: HYP VA range: 4800000000:493fffffff
...
kvm [1]: Hyp mode initialized successfully
which indicates that hyp_va_msb is set, and is always set to the
opposite value of the idmap page to avoid the overlap. This does not
happen with the LX2160A.
Further debugging shows vabits_actual = 39, kva_msb = 38 on LX2160A and
kva_msb = 33 on Armada 8040. Looking at the bit layout of the HYP VA,
there is still one bit available for hyp_va_msb. Set this bit
appropriately. This allows kvm to be functional on the LX2160A, but
without any HYP VA randomisation:
kvm: Limiting the IPA size due to kernel Virtual Address limit
kvm [1]: IPA Size Limit: 43bits
kvm [1]: IDMAP page: 81a24000
kvm [1]: HYP VA range: 4000000000:62ffffffff
...
kvm [1]: Hyp mode initialized successfully
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
---
arch/arm64/kvm/va_layout.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
index 2cf7d4b606c3..83f8b3f51cf4 100644
--- a/arch/arm64/kvm/va_layout.c
+++ b/arch/arm64/kvm/va_layout.c
@@ -22,6 +22,17 @@ static u8 tag_lsb;
static u64 tag_val;
static u64 va_mask;
+/*
+ * We want to generate a hyp VA with the following format:
+ *
+ * 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0
+ * ---------------------------------------------------------
+ * | 0000000 | hyp_va_msb | random tag | kern linear VA |
+ *
+ * which does not conflict with the idmap regions. This means that hyp_va_msb
+ * must always be present. Luckily, when kva_msb == (vabits_actual - 1) we
+ * still have one bit for this, but no bits for the random tag.
+ */
static void compute_layout(void)
{
phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
@@ -39,19 +50,16 @@ static void compute_layout(void)
/*
* No space in the address, let's compute the mask so
* that it covers (vabits_actual - 1) bits, and the region
- * bit. The tag stays set to zero.
+ * bit.
*/
- va_mask = BIT(vabits_actual - 1) - 1;
- va_mask |= hyp_va_msb;
+ tag_lsb = kva_msb;
+ va_mask = BIT(vabits_actual - 1) - 1;
+ tag_val = hyp_va_msb >> tag_lsb;
} else {
/*
* We do have some free bits to insert a random tag.
* Hyp VAs are now created from kernel linear map VAs
* using the following formula (with V == vabits_actual):
- *
- * 63 ... V | V-1 | V-2 .. tag_lsb | tag_lsb - 1 .. 0
- * ---------------------------------------------------------
- * | 0000000 | hyp_va_msb | random tag | kern linear VA |
*/
tag_lsb = kva_msb;
va_mask = GENMASK_ULL(tag_lsb - 1, 0);
--
2.20.1
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