Re: [PATCH v3 3/3] arm/arm64: signal SIBGUS and inject SEA Error

[Christoffer Dall]

On Wed, May 10, 2017 at 05:15:04PM +0800, gengdongjiu wrote:
> Thanks James's explanation.
> 
> Hi Christoffer,
> 
> On 2017/5/9 22:28, James Morse wrote:
> > Hi Christoffer,
> > 
> > On 08/05/17 18:54, Christoffer Dall wrote:
> >> On Mon, May 08, 2017 at 06:28:02PM +0100, James Morse wrote:
> >> I must admit I am losing track of exactly what this proposed API was
> >> supposed to do.
> > 
> > There are two, and we keep jumping between them!
> > This is about two notification methods APEI has for arm64, 'SEA' and 'SEI'.
> > 
> > SEA is synchronous and looks like a data abort. Qemu/kvmtool can inject these
> > today using the KVM_GET/SET_ONE_REG API whenever it wants to.
> > 
> > SEI uses SError, is asynchronous and can be masked. In addition these need to be
> > consumed/synchronised by the ESB instruction, even when executed by a guest.
> > Hardware has the necessary bits to drive all this, we need to expose an API to
> > drive it.
> > 
> > (I try to spell them out each time so I don't confuse SEI with something
> > synchronous!)
> > 
> > 
> > This patch was about SEA. I think you've answered our question:
> 
> we are talking about the SEA(synchronous data abort) injection two methods:
> 
> (1)change vcpu registers in the Qemu/kvmtools and using the KVM_GET/SET_ONE_REG API to set.

Yes, if this is possible, why would you want something more?

> (2)using existed in-kernel API "kvm_inject_dabt" to inject through IOCTL command from Qemu.
> 

I'm not really going to consider this, because "use internal API from
userspace" doesn't work.

So this should be:

  (2) Introduce a new API to do X.

I still think you know what my preference is; use the existing API if at
all possible.

Thanks,
-Christoffer