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KVM: arm64: Prevent mixed-width VM creation

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It looks like we have tolerated creating mixed-width VMs since...
forever. However, that was never the intention, and we'd rather
not have to support that pointless complexity.

Forbid such a setup by making sure all the vcpus have the same
register width.

Reported-by: Steven Price <steven.price@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210524170752.1549797-1-maz@kernel.org
This commit is contained in:
Marc Zyngier 2021-05-24 18:07:52 +01:00
parent e3e880bb15
commit 66e94d5caf
2 changed files with 29 additions and 4 deletions
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5
arch/arm64/include/asm/kvm_emulate.h
View File

@ -463,4 +463,9 @@ static __always_inline void kvm_incr_pc(struct kvm_vcpu *vcpu)
vcpu->arch.flags |= KVM_ARM64_INCREMENT_PC;
}
static inline bool vcpu_has_feature(struct kvm_vcpu *vcpu, int feature)
{
return test_bit(feature, vcpu->arch.features);
}
#endif /* __ARM64_KVM_EMULATE_H__ */

28
arch/arm64/kvm/reset.c
View File

@ -166,6 +166,25 @@ static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
return 0;
}
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)
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;
}
/**
* kvm_reset_vcpu - sets core registers and sys_regs to reset value
* @vcpu: The VCPU pointer
@ -217,13 +236,14 @@ 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 (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1)) {
ret = -EINVAL;
goto out;
}
pstate = VCPU_RESET_PSTATE_SVC;
} else {
pstate = VCPU_RESET_PSTATE_EL1;