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@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_emulate.h | 25 +++++++++++------
arch/arm64/include/asm/kvm_host.h | 8 ++++++
arch/arm64/kvm/arm.c | 41 ++++++++++++++++++++++++++++
arch/arm64/kvm/reset.c | 8 ------
4 files changed, 65 insertions(+), 17 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index d62405ce3e6d..f4f960819888 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -20,6 +20,7 @@
#include <asm/ptrace.h>
#include <asm/cputype.h>
#include <asm/virt.h>
+#include <asm/kvm_mmu.h>
#define CURRENT_EL_SP_EL0_VECTOR 0x0
#define CURRENT_EL_SP_ELx_VECTOR 0x200
@@ -45,7 +46,14 @@ void kvm_vcpu_wfi(struct kvm_vcpu *vcpu);
static __always_inline bool vcpu_el1_is_32bit(struct kvm_vcpu *vcpu)
{
- return !(vcpu->arch.hcr_el2 & HCR_RW);
+ struct kvm *kvm;
+
+ kvm = is_kernel_in_hyp_mode() ? kern_hyp_va(vcpu->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);
}
static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
@@ -72,15 +80,14 @@ 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 11a7ae747ded..5cde7f7b5042 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -125,6 +125,14 @@ struct kvm_arch {
#define KVM_ARCH_FLAG_RETURN_NISV_IO_ABORT_TO_USER 0
/* Memory Tagging Extension enabled for the guest */
#define KVM_ARCH_FLAG_MTE_ENABLED 1
+ /*
+ * The guest's EL1 register width. 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 2
+#define KVM_ARCH_FLAG_EL1_32BIT 3
unsigned long flags;
/*
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 9a2d240ef6a3..9ac75aa46e2f 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1101,6 +1101,43 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
return -EINVAL;
}
+/*
+ * A guest can have either all EL1 32bit or 64bit vcpus only. It is
+ * indicated by a value of KVM_ARCH_FLAG_EL1_32BIT bit in kvm->arch.flags,
+ * which is valid only when KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED in
+ * kvm->arch.flags is set.
+ * This function checks if the vCPU's register width configuration is
+ * consistent with a value of the EL1_32BIT bit in kvm->arch.flags
+ * when the REG_WIDTH_CONFIGURED bit is set.
+ * Otherwise, the function sets a value of EL1_32BIT bit based on the vcpu's
+ * KVM_ARM_VCPU_EL1_32BIT configuration (and sets the REG_WIDTH_CONFIGURED
+ * bit of kvm->arch.flags).
+ */
+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 (test_bit(KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED, &kvm->arch.flags)) {
+ allowed = (is32bit ==
+ test_bit(KVM_ARCH_FLAG_EL1_32BIT, &kvm->arch.flags));
+ } else {
+ if (is32bit)
+ set_bit(KVM_ARCH_FLAG_EL1_32BIT, &kvm->arch.flags);
+
+ set_bit(KVM_ARCH_FLAG_REG_WIDTH_CONFIGURED, &kvm->arch.flags);
+ }
+
+ mutex_unlock(&kvm->lock);
+
+ return allowed ? 0 : -EINVAL;
+}
+
static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
const struct kvm_vcpu_init *init)
{
@@ -1140,6 +1177,10 @@ 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 ecc40c8cd6f6..6c5f7677057d 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -183,9 +183,7 @@ 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;
- unsigned long i;
is32bit = vcpu_has_feature(vcpu, KVM_ARM_VCPU_EL1_32BIT);
if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1) && is32bit)
@@ -195,12 +193,6 @@ 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;
}
--
2.35.1.574.g5d30c73bfb-goog
