Re: [Qemu-arm] [PATCH v2 10/14] target/arm/kvm64: Add kvm_arch_get/put_sve

[Dave Martin]

On Mon, Jun 24, 2019 at 12:55:53PM +0100, Andrew Jones wrote:
> On Mon, Jun 24, 2019 at 12:05:35PM +0100, Dave Martin wrote:
> > On Fri, Jun 21, 2019 at 05:34:18PM +0100, Andrew Jones wrote:
> > > These are the SVE equivalents to kvm_arch_get/put_fpsimd. Note, the
> > > swabbing is different than it is for fpsmid because the vector format
> > > is a little-endian stream of words.
> > 
> > Note, on big-endian hosts the FPSIMD view Vn and the SVE view Zn[127:0]
> > of the FPSIMD/SVE common register bits has the opposite endianness for
> > SVE_{GET,SET}_ONE_REG.
> > 
> > This only matters if mixing the two views: just from this patch I don't
> > know whether this is an issue for QEMU or not.
> 
> I don't know either. My experience with the emulation side of QEMU is
> mostly the zcr_write tweak in this series. And, TBH, I didn't put too
> much thought into the endianness stuff, nor test this series with big
> endian.

Neither did I (at least beyond the "does it boot" level) -- hence the
bug ;)

And of course, few people are using big-endian, so nobody complained.

Just flagging it up so it doesn't get missed!

> Hopefully Richard can chime in on this.

It would be interesting to know whether you do hit this issue
somewhere, or whether you have a strong view about the clarification to
the KVM ABI.

Cheers
---Dave