Re: [PATCH v2 3/6] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched EL0 support

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On 2020-11-09 21:30, Will Deacon wrote:
If a vCPU tries to run 32-bit code on a system with mismatched support

nit: s/tries to run/is caught running/

at EL0, then we should kill it.

Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
 arch/arm64/kvm/arm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 5750ec34960e..d322ac0f4a8e 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -633,6 +633,15 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 	}
 }

+static bool vcpu_mode_is_bad_32bit(struct kvm_vcpu *vcpu)
+{
+	if (likely(!vcpu_mode_is_32bit(vcpu)))
+		return false;
+
+	return !system_supports_32bit_el0() ||
+		static_branch_unlikely(&arm64_mismatched_32bit_el0);
+}
+
 /**
* kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
  * @vcpu:	The VCPU pointer
@@ -816,7 +825,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		 * with the asymmetric AArch32 case), return to userspace with
 		 * a fatal error.
 		 */
-		if (!system_supports_32bit_el0() && vcpu_mode_is_32bit(vcpu)) {
+		if (vcpu_mode_is_bad_32bit(vcpu)) {
 			/*
 			 * As we have caught the guest red-handed, decide that
 			 * it isn't fit for purpose anymore by making the vcpu

Acked-by: Marc Zyngier <maz@xxxxxxxxxx>

        M.
--
Jazz is not dead. It just smells funny...



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