Re: [PATCH v4 17/21] KVM: arm64: Save ESR_EL2 on guest SError

Marc Zyngier
2017-10-31T04:24:33Z

On Thu, Oct 19 2017 at 4:58:03 pm BST, James Morse <james.morse@arm.com> wrote:
> When we exit a guest due to an SError the vcpu fault info isn't updated
> with the ESR. Today this is only done for traps.
>
> The v8.2 RAS Extensions define ISS values for SError. Update the vcpu's
> fault_info with the ESR on SError so that handle_exit() can determine
> if this was a RAS SError and decode its severity.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> arch/arm64/kvm/hyp/switch.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index af37658223a0..cba6d8ac105c 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -230,13 +230,20 @@ static bool __hyp_text __translate_far_to_hpfar(u64 far, u64 *hpfar)
> return true;
> }
>
> +static void __hyp_text __populate_fault_info_esr(struct kvm_vcpu *vcpu)
> +{
> + vcpu->arch.fault.esr_el2 = read_sysreg_el2(esr);
> +}
> +
> static bool __hyp_text __populate_fault_info(struct kvm_vcpu *vcpu)
> {
> - u64 esr = read_sysreg_el2(esr);
> - u8 ec = ESR_ELx_EC(esr);
> + u8 ec;
> + u64 esr;
> u64 hpfar, far;
>
> - vcpu->arch.fault.esr_el2 = esr;
> + __populate_fault_info_esr(vcpu);
> + esr = vcpu->arch.fault.esr_el2;
> + ec = ESR_ELx_EC(esr);
>
> if (ec != ESR_ELx_EC_DABT_LOW && ec != ESR_ELx_EC_IABT_LOW)
> return true;
> @@ -325,6 +332,8 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> */
> if (exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
> goto again;
> + else if (ARM_EXCEPTION_CODE(exit_code) == ARM_EXCEPTION_EL1_SERROR)
> + __populate_fault_info_esr(vcpu);
>
> if (static_branch_unlikely(&vgic_v2_cpuif_trap) &&
> exit_code == ARM_EXCEPTION_TRAP) {

With this patch, the only case were we don't save ESR_EL2 is when we
take an interrupt. I think we should bite the bullet and make it
slightly more streamlined, always saving ESR_EL2.

Thanks,

M.
--
Jazz is not dead. It just smells funny.