Re: [PATCH v7 22/22] Documentation: arm64: describe asymmetric 32-bit support
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From: Marc Zyngier <maz@kernel.org>
Date: 2021-05-25 17:14:04
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On Tue, 25 May 2021 16:14:32 +0100, Will Deacon [off-list ref] wrote:
Document support for running 32-bit tasks on asymmetric 32-bit systems and its impact on the user ABI when enabled. Signed-off-by: Will Deacon <will@kernel.org> --- .../admin-guide/kernel-parameters.txt | 3 + Documentation/arm64/asymmetric-32bit.rst | 154 ++++++++++++++++++ Documentation/arm64/index.rst | 1 + 3 files changed, 158 insertions(+) create mode 100644 Documentation/arm64/asymmetric-32bit.rst
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+KVM +--- + +Although KVM will not advertise 32-bit EL0 support to any vCPUs on an +asymmetric system, a broken guest at EL1 could still attempt to execute +32-bit code at EL0. In this case, an exit from a vCPU thread in 32-bit +mode will return to host userspace with an ``exit_reason`` of +``KVM_EXIT_FAIL_ENTRY``.
Nit: there is a bit more to it. The vcpu will be left in a permanent non-runnable state until KVM_ARM_VCPU_INIT is issued to reset the vcpu into a saner state. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel