On Tue, 25 May 2021 16:14:32 +0100, Will Deacon <will@xxxxxxxxxx> 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@xxxxxxxxxx> > --- > .../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 > [...] > +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.
