Re: [PATCH v2 2/5] KVM: arm64: Get rid of host SVE tracking/saving

Mark Brown
2021-11-22T17:58:08Z

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On Mon, Nov 22, 2021 at 03:57:32PM +0000, Marc Zyngier wrote:
> Zenghui Yu <yuzenghui@huawei.com> wrote:

> > Nit: This removes the only user of __sve_save_state() helper. Should we
> > still keep it in fpsimd.S?

> I was in two minds about that, as I'd like to eventually be able to
> use SVE for protected guests, where the hypervisor itself has to be in
> charge of the FP/SVE save-restore.

> But that's probably several months away, and I can always revert a
> deletion patch if I need to, so let's get rid of it now.

While we're on the subject of potential future work we might in future
want to not disable SVE on every syscall if (as seems likely) it turns
out that that's more performant for small vector lengths which would
mean some minor reshuffling here to do something like convert the saved
state to FPSIMD and drop TIF_SVE in _vcpu_load_fp(). As with using SVE
in protected guests that can just be done when needed though.

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