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authorReiji Watanabe <reijiw@google.com>2022-03-28 20:19:23 -0700
committerMarc Zyngier <maz@kernel.org>2022-04-06 12:29:45 +0100
commit26bf74bd9f6ff0f1545b4f0c92a37c232d076014 (patch)
tree759d1aa56c57f78817cca50264eb2ddd015dc941 /arch
parentc707663e81ef48d279719e97fd86acef835a2671 (diff)
KVM: arm64: mixed-width check should be skipped for uninitialized vCPUs
KVM allows userspace to configure either all EL1 32bit or 64bit vCPUs for a guest. At vCPU reset, vcpu_allowed_register_width() checks if the vcpu's register width is consistent with all other vCPUs'. Since the checking is done even against vCPUs that are not initialized (KVM_ARM_VCPU_INIT has not been done) yet, the uninitialized vCPUs are erroneously treated as 64bit vCPU, which causes the function to incorrectly detect a mixed-width VM. Introduce KVM_ARCH_FLAG_EL1_32BIT and KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED bits for kvm->arch.flags. A value of the EL1_32BIT bit indicates that the guest needs to be configured with all 32bit or 64bit vCPUs, and a value of the REG_WIDTH_CONFIGURED bit indicates if a value of the EL1_32BIT bit is valid (already set up). Values in those bits are set at the first KVM_ARM_VCPU_INIT for the guest based on KVM_ARM_VCPU_EL1_32BIT configuration for the vCPU. Check vcpu's register width against those new bits at the vcpu's KVM_ARM_VCPU_INIT (instead of against other vCPUs' register width). Fixes: 66e94d5cafd4 ("KVM: arm64: Prevent mixed-width VM creation") Signed-off-by: Reiji Watanabe <reijiw@google.com> Reviewed-by: Oliver Upton <oupton@google.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220329031924.619453-2-reijiw@google.com
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/include/asm/kvm_emulate.h27
-rw-r--r--arch/arm64/include/asm/kvm_host.h10
-rw-r--r--arch/arm64/kvm/reset.c65
3 files changed, 74 insertions, 28 deletions
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index d62405ce3e6d..7496deab025a 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -43,10 +43,22 @@ void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
void kvm_vcpu_wfi(struct kvm_vcpu *vcpu);
+#if defined(__KVM_VHE_HYPERVISOR__) || defined(__KVM_NVHE_HYPERVISOR__)
static __always_inline bool vcpu_el1_is_32bit(struct kvm_vcpu *vcpu)
{
return !(vcpu->arch.hcr_el2 & HCR_RW);
}
+#else
+static __always_inline bool vcpu_el1_is_32bit(struct kvm_vcpu *vcpu)
+{
+ struct kvm *kvm = vcpu->kvm;
+
+ WARN_ON_ONCE(!test_bit(KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED,
+ &kvm->arch.flags));
+
+ return test_bit(KVM_ARCH_FLAG_EL1_32BIT, &kvm->arch.flags);
+}
+#endif
static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
{
@@ -72,15 +84,14 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
vcpu->arch.hcr_el2 |= HCR_TVM;
}
- if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features))
+ if (vcpu_el1_is_32bit(vcpu))
vcpu->arch.hcr_el2 &= ~HCR_RW;
-
- /*
- * TID3: trap feature register accesses that we virtualise.
- * For now this is conditional, since no AArch32 feature regs
- * are currently virtualised.
- */
- if (!vcpu_el1_is_32bit(vcpu))
+ else
+ /*
+ * TID3: trap feature register accesses that we virtualise.
+ * For now this is conditional, since no AArch32 feature regs
+ * are currently virtualised.
+ */
vcpu->arch.hcr_el2 |= HCR_TID3;
if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e3b25dc6c367..94a27a7520f4 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -127,6 +127,16 @@ struct kvm_arch {
#define KVM_ARCH_FLAG_MTE_ENABLED 1
/* At least one vCPU has ran in the VM */
#define KVM_ARCH_FLAG_HAS_RAN_ONCE 2
+ /*
+ * The following two bits are used to indicate the guest's EL1
+ * register width configuration. A value of KVM_ARCH_FLAG_EL1_32BIT
+ * bit is valid only when KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED is set.
+ * Otherwise, the guest's EL1 register width has not yet been
+ * determined yet.
+ */
+#define KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED 3
+#define KVM_ARCH_FLAG_EL1_32BIT 4
+
unsigned long flags;
/*
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index ecc40c8cd6f6..6c70c6f61c70 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -181,27 +181,51 @@ static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
return 0;
}
-static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu)
+/**
+ * kvm_set_vm_width() - set the register width for the guest
+ * @vcpu: Pointer to the vcpu being configured
+ *
+ * Set both KVM_ARCH_FLAG_EL1_32BIT and KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED
+ * in the VM flags based on the vcpu's requested register width, the HW
+ * capabilities and other options (such as MTE).
+ * When REG_WIDTH_CONFIGURED is already set, the vcpu settings must be
+ * consistent with the value of the FLAG_EL1_32BIT bit in the flags.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int kvm_set_vm_width(struct kvm_vcpu *vcpu)
{
- struct kvm_vcpu *tmp;
+ struct kvm *kvm = vcpu->kvm;
bool is32bit;
- unsigned long i;
is32bit = vcpu_has_feature(vcpu, KVM_ARM_VCPU_EL1_32BIT);
+
+ lockdep_assert_held(&kvm->lock);
+
+ if (test_bit(KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED, &kvm->arch.flags)) {
+ /*
+ * The guest's register width is already configured.
+ * Make sure that the vcpu is consistent with it.
+ */
+ if (is32bit == test_bit(KVM_ARCH_FLAG_EL1_32BIT, &kvm->arch.flags))
+ return 0;
+
+ return -EINVAL;
+ }
+
if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1) && is32bit)
- return false;
+ return -EINVAL;
/* MTE is incompatible with AArch32 */
- if (kvm_has_mte(vcpu->kvm) && is32bit)
- return false;
+ if (kvm_has_mte(kvm) && is32bit)
+ return -EINVAL;
- /* Check that the vcpus are either all 32bit or all 64bit */
- kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
- if (vcpu_has_feature(tmp, KVM_ARM_VCPU_EL1_32BIT) != is32bit)
- return false;
- }
+ if (is32bit)
+ set_bit(KVM_ARCH_FLAG_EL1_32BIT, &kvm->arch.flags);
- return true;
+ set_bit(KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED, &kvm->arch.flags);
+
+ return 0;
}
/**
@@ -230,10 +254,16 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
u32 pstate;
mutex_lock(&vcpu->kvm->lock);
- reset_state = vcpu->arch.reset_state;
- WRITE_ONCE(vcpu->arch.reset_state.reset, false);
+ ret = kvm_set_vm_width(vcpu);
+ if (!ret) {
+ reset_state = vcpu->arch.reset_state;
+ WRITE_ONCE(vcpu->arch.reset_state.reset, false);
+ }
mutex_unlock(&vcpu->kvm->lock);
+ if (ret)
+ return ret;
+
/* Reset PMU outside of the non-preemptible section */
kvm_pmu_vcpu_reset(vcpu);
@@ -260,14 +290,9 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
}
}
- if (!vcpu_allowed_register_width(vcpu)) {
- ret = -EINVAL;
- goto out;
- }
-
switch (vcpu->arch.target) {
default:
- if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) {
+ if (vcpu_el1_is_32bit(vcpu)) {
pstate = VCPU_RESET_PSTATE_SVC;
} else {
pstate = VCPU_RESET_PSTATE_EL1;