On Wed, Aug 05, 2020 at 03:33:22PM +0100, James Morse wrote:
> Hi Andrew,
>
> On 30/07/2020 16:18, Andrew Scull wrote:
> > The ESB at the start of the vectors causes any SErrors to be consumed to
> > DISR_EL1. If the exception came from the host and the ESB caught an
> > SError, it would not be noticed until a guest exits and DISR_EL1 is
> > checked. Further, the SError would be attributed to the guest and not
> > the host.
>
> Yup, this happens because the world has moved underneath this code:
That's understandable!
> Previously any v8.2 RAS capable system would have been crazy to turn off VHE, so v8.0 and
> v8.1 systems had a nop here instead, and v8.2 systems had VHE, so there were no 'from the
> host' EL2 vectors.
RAS with nVHE is a buildable config and we're being foolish enough to
think about it so hopefully we can work something out :)
> > To avoid these problems, use a different exception vector for the host
> > that does not use an ESB but instead leaves any host SError pending. A
> > guest will not be entered if an SError is pending so it will always be
> > the host that will receive and handle it.
> >
> > Hyp initialization is now passed the vector that is used for the host
> > and the vector for guests is stored in a percpu variable as
> > kvm_get_hyp_vector() is not suitable for calling from nVHE hyp.
>
> > Fixes: 0e5b9c085dce ("KVM: arm64: Consume pending SError as early as possible")
>
> Surely this can only happen if you had turned VHE off?
Correct, I'll make that clearer in the description.
> Thanks,
>
> James
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