Re: [PATCH v4 20/21] KVM: arm64: Take any host SError before entering the guest

James Morse
2017-11-03T16:14:09Z

Hi Christoffer,

On 03/11/17 12:49, Christoffer Dall wrote:
> Does a non-secure esb() cause the error to be delivered to firmware on
> the secure side if anything is pending?

Yes, the ESB-instruction causes 'synchronisable' errors to become pending as an
SError. They then follow the normal SError rules.

> I'm not sure I fully understand the interaction between issuing an
> esb() in non-secure and firmware handling a RAS error; I thought there
> would be none, and that this was only for kernel-first ?

To implement firmware-first, EL3 has to set SCR_EL3.EA to route external-aborts
and physical SError to EL3. So an ESB-instruction, even in a guest, may cause an
SError to be taken to EL3 for firmware-first handling.

This is why RAS is causing so much noise for KVM, any notification could also
interrupt a guest, so firmware has to emulate an exception taken to EL2
correctly and KVM will have to plumb the notification across to the host APEI code.

Thanks,

James