On Thu, 18 Mar 2021 14:13:58 +0000, Will Deacon <[email protected]> wrote: > > On Thu, Mar 18, 2021 at 12:25:31PM +0000, Marc Zyngier wrote: > > Implement the SVE save/restore for nVHE, following a similar > > logic to that of the VHE implementation: > > > > - the SVE state is switched on trap from EL1 to EL2 > > > > - no further changes to ZCR_EL2 occur as long as the guest isn't > > preempted or exit to userspace > > > > - ZCR_EL2 is reset to its default value on the first SVE access from > > the host EL1, and ZCR_EL1 restored to the default guest value in > > vcpu_put() > > > > Signed-off-by: Marc Zyngier <[email protected]> > > --- > > arch/arm64/kvm/fpsimd.c | 10 +++++-- > > arch/arm64/kvm/hyp/include/hyp/switch.h | 37 +++++++++---------------- > > arch/arm64/kvm/hyp/nvhe/switch.c | 4 +-- > > 3 files changed, 23 insertions(+), 28 deletions(-) > > > > diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c > > index 14ea05c5134a..5621020b28de 100644 > > --- a/arch/arm64/kvm/fpsimd.c > > +++ b/arch/arm64/kvm/fpsimd.c > > @@ -121,11 +121,17 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) > > local_irq_save(flags); > > > > if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) { > > - if (guest_has_sve) > > + if (guest_has_sve) { > > __vcpu_sys_reg(vcpu, ZCR_EL1) = > > read_sysreg_el1(SYS_ZCR); > > > > + /* Restore the VL that was saved when bound to the CPU > > */ > > + if (!has_vhe()) > > + sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - > > 1, > > + SYS_ZCR_EL1); > > You end up reading ZCR_EL1 twice here, but it's probably not the end of the > world.
True, but I'd expect read accesses to ZCR_EL1 to be reasonably fast, something we can't expect from writes. > > Anyway: > > Acked-by: Will Deacon <[email protected]> Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
