arm64/cpufeature: Validate hypervisor capabilities during CPU hotplug

This validates hypervisor capabilities like VMID width, IPA range for any
hot plug CPU against system finalized values. KVM's view of the IPA space
is used while allowing a given CPU to come up. While here, it factors out
get_vmid_bits() for general use.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: kvmarm@lists.cs.columbia.edu
Cc: linux-kernel@vger.kernel.org

Suggested-by: Suzuki Poulose <suzuki.poulose@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/1589248647-22925-1-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

4 files changed, 56 insertions, 1 deletions

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index f5c4672e498b..928814d35669 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -752,6 +752,24 @@ static inline bool cpu_has_hw_af(void)
 extern bool cpu_has_amu_feat(int cpu);
 #endif
 
+static inline unsigned int get_vmid_bits(u64 mmfr1)
+{
+	int vmid_bits;
+
+	vmid_bits = cpuid_feature_extract_unsigned_field(mmfr1,
+						ID_AA64MMFR1_VMIDBITS_SHIFT);
+	if (vmid_bits == ID_AA64MMFR1_VMIDBITS_16)
+		return 16;
+
+	/*
+	 * Return the default here even if any reserved
+	 * value is fetched from the system register.
+	 */
+	return 8;
+}
+
+u32 get_kvm_ipa_limit(void);
+
 #endif /* __ASSEMBLY__ */
 
 #endif
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 30b0e8d6b895..a7137e144b97 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -416,7 +416,7 @@ static inline unsigned int kvm_get_vmid_bits(void)
 {
 	int reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
 
-	return (cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR1_VMIDBITS_SHIFT) == 2) ? 16 : 8;
+	return get_vmid_bits(reg);
 }
 
 /*
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9b05843d67af..be8a634abdd4 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2315,6 +2315,35 @@ static void verify_sve_features(void)
 	/* Add checks on other ZCR bits here if necessary */
 }
 
+static void verify_hyp_capabilities(void)
+{
+	u64 safe_mmfr1, mmfr0, mmfr1;
+	int parange, ipa_max;
+	unsigned int safe_vmid_bits, vmid_bits;
+
+	if (!IS_ENABLED(CONFIG_KVM) || !IS_ENABLED(CONFIG_KVM_ARM_HOST))
+		return;
+
+	safe_mmfr1 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
+	mmfr0 = read_cpuid(ID_AA64MMFR0_EL1);
+	mmfr1 = read_cpuid(ID_AA64MMFR1_EL1);
+
+	/* Verify VMID bits */
+	safe_vmid_bits = get_vmid_bits(safe_mmfr1);
+	vmid_bits = get_vmid_bits(mmfr1);
+	if (vmid_bits < safe_vmid_bits) {
+		pr_crit("CPU%d: VMID width mismatch\n", smp_processor_id());
+		cpu_die_early();
+	}
+
+	/* Verify IPA range */
+	parange = mmfr0 & 0x7;
+	ipa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
+	if (ipa_max < get_kvm_ipa_limit()) {
+		pr_crit("CPU%d: IPA range mismatch\n", smp_processor_id());
+		cpu_die_early();
+	}
+}
 
 /*
  * Run through the enabled system capabilities and enable() it on this CPU.
@@ -2340,6 +2369,9 @@ static void verify_local_cpu_capabilities(void)
 
 	if (system_supports_sve())
 		verify_sve_features();
+
+	if (is_hyp_mode_available())
+		verify_hyp_capabilities();
 }
 
 void check_local_cpu_capabilities(void)
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 102e5c4e01a0..d4eb6612bb3c 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -332,6 +332,11 @@ out:
 	return ret;
 }
 
+u32 get_kvm_ipa_limit(void)
+{
+	return kvm_ipa_limit;
+}
+
 void kvm_set_ipa_limit(void)
 {
 	unsigned int ipa_max, pa_max, va_max, parange;