[PATCH V3] arm64/cpufeature: Validate hypervisor capabilities during CPU hotplug

* [PATCH V3] arm64/cpufeature: Validate hypervisor capabilities during CPU hotplug
@ 2020-05-12  1:57 Anshuman Khandual
  2020-05-20 17:54 ` Will Deacon
  0 siblings, 1 reply; 3+ messages in thread
From: Anshuman Khandual @ 2020-05-12  1:57 UTC (permalink / raw)
  To: linux-arm-kernel
  Cc: Anshuman Khandual, Catalin Marinas, linux-kernel, Marc Zyngier,
	Will Deacon, kvmarm

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

Reviewed-by: Marc Zyngier <maz@kernel.org>
Suggested-by: Suzuki Poulose <suzuki.poulose@arm.com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V3:

- Dropped "#ifdef CONFIG_KVM_ARM_HOST" per Marc
- Dropped ID_AA64MMFR0_PARANGE_MASK (for now)
- Updated the commit message per Marc

Changes in V2: (https://patchwork.kernel.org/patch/11535359/)

- Added is_hyp_mode_available() check per Marc
- Moved verify_kvm_capabilities() into cpufeature.c per Marc
- Added helper get_kvm_ipa_limit() to fetch kvm_ipa_limit per Marc
- Renamed kvm as hyp including the commit message per Marc

Changes in V1: (https://patchwork.kernel.org/patch/11532565/)

 arch/arm64/include/asm/cpufeature.h | 18 ++++++++++++++++
 arch/arm64/include/asm/kvm_mmu.h    |  2 +-
 arch/arm64/kernel/cpufeature.c      | 33 +++++++++++++++++++++++++++++
 arch/arm64/kvm/reset.c              |  5 +++++
 4 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index afe08251ff95..1291ad5a9ccb 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -745,6 +745,24 @@ 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 9fac745aa7bb..30917fe7942a 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2181,6 +2181,36 @@ static void verify_sve_features(void)
 	/* Add checks on other ZCR bits here if necessary */
 }
 
+#ifdef CONFIG_KVM_ARM_HOST
+void verify_hyp_capabilities(void)
+{
+	u64 safe_mmfr1, mmfr0, mmfr1;
+	int parange, ipa_max;
+	unsigned int safe_vmid_bits, vmid_bits;
+
+	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();
+	}
+}
+#else	/* !CONFIG_KVM_ARM_HOST */
+static inline void verify_hyp_capabilities(void) { }
+#endif	/* CONFIG_KVM_ARM_HOST */
 
 /*
  * Run through the enabled system capabilities and enable() it on this CPU.
@@ -2206,6 +2236,9 @@ 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 30b7ea680f66..841b492ff334 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -340,6 +340,11 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 	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;
-- 
2.20.1

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