[PATCH v3 2/3] arm64: kvm: inject SError with virtual syndrome

[gengdongjiu]

2017-05-13 1:24 GMT+08:00, James Morse <james.morse at arm.com>:
> Hi gengdongjiu,
>
> On 05/05/17 14:19, gengdongjiu wrote:
>> On 2017/5/2 23:37, James Morse wrote:
>> > ... I think you expect an SError to arrive at EL2 and have its ESR
>> > recorded in
>> > vcpu->arch.fault.vsesr_el2. Some time later KVM decides to inject an
>> > SError into
>> > the guest, and this ESR is reused...
>> >
>> > We shouldn't do this. Qemu/kvmtool may want to inject a virtual-SError
>> > that
>> > never started as a physical-SError. Qemu/kvmtool may choose to notify
>> > the guest
>> > of RAS events via another mechanism, or not at all.
>> >
>> > KVM should not give the guest an ESR value of its choice. For SError the
>> > ESR
>> > describes whether the error is corrected, correctable or fatal.
>> > Qemu/kvmtool
>> > must choose this.
>
>> Below is my previous solution:
>> For the SError, CPU will firstly trap to EL3 firmware and records the
>> syndrome to ESR_EL3.
>> Before jumping to El2 hypervisors, it will copy the esr_el3 to esr_el2.
>
> (Copying the ESR value won't always be the right thing to do.)
  James,  thanks for your kindly explanation, understand you  thought.

>
>
>> so in order to pass this syndrome to vsesr_el2, using the esr_el2 value to
>> assign it.
>
>> If Qemu/kvmtool chooses the ESR value and ESR only describes whether the
>> error is corrected/correctable/fatal,
>> whether the information is not enough for the guest?
>
> So the API should specify which of these three severities to use? I think
> this
> is too specific. The API should be useful for anything the VSE/VSESR
> hardware
> can do.
>
> VSESR_EL2 is described in the RAS spec: 4.4.12 [0], its a 64 bit register.
> I
> think we should let Qemu/kvmtool specify any 64bit value here, but KVM
> should
> reject values that try to set bits described as RES0.
>
> This would let Qemu/kvmtool specify any SError ISS, either setting
> ESR_ELx.IDS
> and some virtual-machine specific value, or encoding any severity in AET
> and
> choosing the DFSC/EA bits appropriately.
   it sounds reasonable

>
>
>>> > I think we need an API that allows Qemu/kvmtool to inject SError into a
>>> > guest,
>>> > but that isn't quite what you have here.
>
>> KVM provides APIs to inject the SError, Qemu/kvmtool call the API though
>> IOCTL, may be OK?
>
> (just the one API call), yes.
   Ok, have added.

>
>
> Thanks,
>
> James
>
> [0]
> https://static.docs.arm.com/ddi0587/a/RAS%20Extension-release%20candidate_march_29.pdf
>
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