On Sat, 01 Jun 2024 00:13:50 +0100,
Oliver Upton <oliver.upton@xxxxxxxxx> wrote:
>
> Round out the ZCR_EL2 gymnastics by loading SVE state in the fast path
> when the guest hypervisor tries to access SVE state.
>
> Signed-off-by: Oliver Upton <oliver.upton@xxxxxxxxx>
> ---
> arch/arm64/kvm/hyp/include/hyp/switch.h | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
> index 428ee15dd6ae..5872eaafc7f0 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
> @@ -345,6 +345,10 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
> if (guest_hyp_fpsimd_traps_enabled(vcpu))
> return false;
> break;
> + case ESR_ELx_EC_SYS64:
> + if (WARN_ON_ONCE(!is_hyp_ctxt(vcpu)))
> + return false;
> + fallthrough;
> case ESR_ELx_EC_SVE:
> if (!sve_guest)
> return false;
> @@ -520,6 +524,22 @@ static bool handle_ampere1_tcr(struct kvm_vcpu *vcpu)
> return true;
> }
>
> +static bool kvm_hyp_handle_zcr(struct kvm_vcpu *vcpu, u64 *exit_code)
> +{
> + u32 sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu));
> +
> + if (!vcpu_has_nv(vcpu))
> + return false;
> +
> + if (sysreg != SYS_ZCR_EL2)
> + return false;
> +
> + if (guest_owns_fp_regs())
> + return false;
> +
> + return kvm_hyp_handle_fpsimd(vcpu, exit_code);
For my own understanding of the flow: let's say the L1 guest accesses
ZCR_EL2 while the host own the FP regs:
- ZCR_EL2 traps
- we restore the guest's state, enable SVE
- ZCR_EL2 traps again
- emulate the access on the slow path
In contrast, the same thing using ZCR_EL1 in L1 results in:
- ZCR_EL1 traps
- we restore the guest's state, enable SVE
and we're done.
Is that correct? If so, a comment would help... ;-)
> +}
> +
> static bool kvm_hyp_handle_sysreg(struct kvm_vcpu *vcpu, u64 *exit_code)
> {
> if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM) &&
> @@ -537,6 +557,9 @@ static bool kvm_hyp_handle_sysreg(struct kvm_vcpu *vcpu, u64 *exit_code)
> if (kvm_hyp_handle_cntpct(vcpu))
> return true;
>
> + if (kvm_hyp_handle_zcr(vcpu, exit_code))
> + return true;
> +
> return false;
> }
>
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
