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

From: [email-masked] (Marc Zyngier)
Date: Tue, 31 Oct 2017 04:26:01 +0000

On Thu, Oct 19 2017 at  4:58:03 pm BST, James Morse <[email-masked]> 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 <[email-masked]>
> ---
>  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.