KVM allows userspace to configure either all 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 a new flag (el1_reg_width) in kvm_arch to indicates that
the guest needs to be configured with all 32bit or 64bit vCPUs,
and initialize it at the first KVM_ARM_VCPU_INIT for the guest.
Check vcpu's register width against the flag 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@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_host.h | 13 +++++++++++++
arch/arm64/kvm/arm.c | 30 ++++++++++++++++++++++++++++++
arch/arm64/kvm/reset.c | 8 --------
3 files changed, 43 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2a5f7f38006f..c02b7caf2c82 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -102,6 +102,12 @@ struct kvm_s2_mmu {
struct kvm_arch_memory_slot {
};
+enum kvm_el1_reg_width {
+ EL1_WIDTH_UNINITIALIZED = 0,
+ EL1_32BIT,
+ EL1_64BIT,
+};
+
struct kvm_arch {
struct kvm_s2_mmu mmu;
@@ -137,6 +143,13 @@ struct kvm_arch {
/* Memory Tagging Extension enabled for the guest */
bool mte_enabled;
+
+ /*
+ * EL1 register width for the guest.
+ * This is set at the first KVM_ARM_VCPU_INIT for the guest based
+ * on whether the vcpu has KVM_ARM_VCPU_EL1_32BIT or not.
+ */
+ enum kvm_el1_reg_width el1_reg_width;
};
struct kvm_vcpu_fault_info {
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index e4727dc771bf..54ae8bf9d187 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1058,6 +1058,32 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
return -EINVAL;
}
+/*
+ * A guest can have either all 32bit or 64bit vcpus only.
+ * Either one the guest has is indicated in kvm->arch.el1_reg_width.
+ * Check if the vcpu's register width is consistent with
+ * kvm->arch.el1_reg_width. If kvm->arch.el1_reg_width is not set yet,
+ * set it based on the vcpu's KVM_ARM_VCPU_EL1_32BIT configuration.
+ */
+static int kvm_register_width_check_or_init(struct kvm_vcpu *vcpu)
+{
+ bool is32bit;
+ bool allowed = true;
+ struct kvm *kvm = vcpu->kvm;
+
+ is32bit = vcpu_has_feature(vcpu, KVM_ARM_VCPU_EL1_32BIT);
+
+ mutex_lock(&kvm->lock);
+
+ if (kvm->arch.el1_reg_width == EL1_WIDTH_UNINITIALIZED)
+ kvm->arch.el1_reg_width = is32bit ? EL1_32BIT : EL1_64BIT;
+ else
+ allowed = (is32bit == (kvm->arch.el1_reg_width == EL1_32BIT));
+
+ mutex_unlock(&kvm->lock);
+ return allowed ? 0 : -EINVAL;
+}
+
static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
const struct kvm_vcpu_init *init)
{
@@ -1097,6 +1123,10 @@ static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
/* Now we know what it is, we can reset it. */
ret = kvm_reset_vcpu(vcpu);
+
+ if (!ret)
+ ret = kvm_register_width_check_or_init(vcpu);
+
if (ret) {
vcpu->arch.target = -1;
bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES);
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 426bd7fbc3fd..dbf2939a6a96 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -168,9 +168,7 @@ static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu)
{
- struct kvm_vcpu *tmp;
bool is32bit;
- int i;
is32bit = vcpu_has_feature(vcpu, KVM_ARM_VCPU_EL1_32BIT);
if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1) && is32bit)
@@ -180,12 +178,6 @@ static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu)
if (kvm_has_mte(vcpu->kvm) && is32bit)
return false;
- /* 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;
- }
-
return true;
}
base-commit: 37144b2c855f9311c72f292125061d4a52d02856
--
2.34.1.703.g22d0c6ccf7-goog
