[PATCH v3 21/21] KVM: arm64: Don't constrain maximum IPA size based on host configuration

Will Deacon
2020-08-25T09:47:22Z

Now that the guest stage-2 page-tables are managed independently from
the host stage-1 page-tables, we can avoid constraining the IPA size
based on the host and instead limit it only based on the PARange field
of the ID_AA64MMFR0 register.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
arch/arm64/kvm/reset.c | 38 +++++---------------------------------
1 file changed, 5 insertions(+), 33 deletions(-)

diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index ee33875c5c2a..471ee9234e40 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -339,7 +339,7 @@ u32 get_kvm_ipa_limit(void)

int kvm_set_ipa_limit(void)
{
- unsigned int ipa_max, pa_max, va_max, parange, tgran_2;
+ unsigned int parange, tgran_2;
u64 mmfr0;

mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
@@ -376,38 +376,10 @@ int kvm_set_ipa_limit(void)
break;
}

- pa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
-
- /* Clamp the IPA limit to the PA size supported by the kernel */
- ipa_max = (pa_max > PHYS_MASK_SHIFT) ? PHYS_MASK_SHIFT : pa_max;
- /*
- * Since our stage2 table is dependent on the stage1 page table code,
- * we must always honor the following condition:
- *
- * Number of levels in Stage1 >= Number of levels in Stage2.
- *
- * So clamp the ipa limit further down to limit the number of levels.
- * Since we can concatenate upto 16 tables at entry level, we could
- * go upto 4bits above the maximum VA addressable with the current
- * number of levels.
- */
- va_max = PGDIR_SHIFT + PAGE_SHIFT - 3;
- va_max += 4;
-
- if (va_max < ipa_max)
- ipa_max = va_max;
-
- /*
- * If the final limit is lower than the real physical address
- * limit of the CPUs, report the reason.
- */
- if (ipa_max < pa_max)
- pr_info("kvm: Limiting the IPA size due to kernel %s Address limit\n",
- (va_max < pa_max) ? "Virtual" : "Physical");
-
- WARN(ipa_max < KVM_PHYS_SHIFT,
- "KVM IPA limit (%d bit) is smaller than default size\n", ipa_max);
- kvm_ipa_limit = ipa_max;
+ kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange);
+ WARN(kvm_ipa_limit < KVM_PHYS_SHIFT,
+ "KVM IPA limit (%d bit) is smaller than default size\n",
+ kvm_ipa_limit);
kvm_info("IPA Size Limit: %dbits\n", kvm_ipa_limit);

return 0;
--
2.28.0.297.g1956fa8f8d-goog