[PATCH v2] KVM: arm64: Constrain the host to the maximum shared SVE VL with pKVM

[Mark Brown]

On Thu, Sep 12, 2024 at 03:21:43PM +0100, Fuad Tabba wrote:

> One part that you haven't changed is setting ZCR_EL2 during el2 setup:
> arch/arm64/include/asm/el2_setup.h: .Linit_sve_ : lines 290/291

> I guess at that point it's not straightforward to figure sve_max_vl.
> Is there a window after el2 setup where we might actually get the VL
> implied by ZCR_ELx_LEN_MASK, or would it always get set to
> sve_vq_from_vl(kvm_host_sve_max_vl) - 1 ?

Yeah, at that point we have no idea what any other cores might look like
and there's just generally a bootstrapping issue - we need to see the
actual maximum VLs for the PEs to work out what the maximum VL for the
system is so we can tell KVM what to enforce.
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