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

[Andrew Jones]

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.

Hopefully Richard can chime in on this.

Thanks,
drew

> 
> The kernel and gdb were recently found to be broken in this regard for
> userspace [1] but the KVM interface should be unaffected.
> 
> Cheers
> ---Dave
> 
> [1] 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/arm64/kernel?id=41040cf7c5f0f26c368bc5d3016fed3a9ca6dba4