KVM: arm64: Don't constrain maximum IPA size based on host configuration

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.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Link: https://lore.kernel.org/r/20200911132529.19844-22-will@kernel.org

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);
@@ -376,39 +376,11 @@ 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_info("IPA Size Limit: %dbits\n", kvm_ipa_limit);
+	kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange);
+	WARN(kvm_ipa_limit < KVM_PHYS_SHIFT,
+	     "KVM IPA Size Limit (%d bits) is smaller than default size\n",
+	     kvm_ipa_limit);
+	kvm_info("IPA Size Limit: %d bits\n", kvm_ipa_limit);
 
 	return 0;
 }