KVM: arm64: Handle Asymmetric AArch32 systems
On a system without uniform support for AArch32 at EL0, it is possible for the guest to force run AArch32 at EL0 and potentially cause an illegal exception if running on a core without AArch32. Add an extra check so that if we catch the guest doing that, then we prevent it from running again by resetting vcpu->arch.target and return ARM_EXCEPTION_IL. We try to catch this misbehaviour as early as possible and not rely on an illegal exception occuring to signal the problem. Attempting to run a 32bit app in the guest will produce an error from QEMU if the guest exits while running in AArch32 EL0. Tested on Juno by instrumenting the host to fake asym aarch32 and instrumenting KVM to make the asymmetry visible to the guest. [will: Incorporated feedback from Marc] Signed-off-by:Qais Yousef <qais.yousef@arm.com> Signed-off-by:
Will Deacon <will@kernel.org> Signed-off-by:
Marc Zyngier <maz@kernel.org> Cc: James Morse <james.morse@arm.com> Cc: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20201021104611.2744565-2-qais.yousef@arm.com Link: https://lore.kernel.org/r/20201027215118.27003-2-will@kernel.org
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