[PATCH 01/11] KVM: arm64: Don't adjust PC on SError during SMC trap

[Mark Rutland]

On Mon, Oct 26, 2020 at 01:34:40PM +0000, Marc Zyngier wrote:
> On SMC trap, the prefered return address is set to that of the SMC
> instruction itself. It is thus wrong to tyr and roll it back when

Typo: s/tyr/try/

> an SError occurs while trapping on SMC. It is still necessary on
> HVC though, as HVC doesn't cause a trap, and sets ELR to returning
> *after* the HVC.
> 
> It also became apparent that the is 16bit encoding for an AArch32

I guess s/that the is/that there is no/ ?

> HVC instruction, meaning that the displacement is always 4 bytes,
> no matter what the ISA is. Take this opportunity to simplify it.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>

Assuming that there is no 16-bit HVC:

Acked-by: Mark Rutland <mark.rutland at arm.com>

Mark.

> ---
>  arch/arm64/kvm/handle_exit.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 5d690d60ccad..79a720657c47 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -245,15 +245,15 @@ int handle_exit(struct kvm_vcpu *vcpu, int exception_index)
>  		u8 esr_ec = ESR_ELx_EC(kvm_vcpu_get_esr(vcpu));
>  
>  		/*
> -		 * HVC/SMC already have an adjusted PC, which we need
> -		 * to correct in order to return to after having
> -		 * injected the SError.
> +		 * HVC already have an adjusted PC, which we need to
> +		 * correct in order to return to after having injected
> +		 * the SError.
> +		 *
> +		 * SMC, on the other hand, is *trapped*, meaning its
> +		 * preferred return address is the SMC itself.
>  		 */
> -		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64 ||
> -		    esr_ec == ESR_ELx_EC_SMC32 || esr_ec == ESR_ELx_EC_SMC64) {
> -			u32 adj =  kvm_vcpu_trap_il_is32bit(vcpu) ? 4 : 2;
> -			*vcpu_pc(vcpu) -= adj;
> -		}
> +		if (esr_ec == ESR_ELx_EC_HVC32 || esr_ec == ESR_ELx_EC_HVC64)
> +			*vcpu_pc(vcpu) -= 4;
>  
>  		return 1;
>  	}
> -- 
> 2.28.0
> 
> _______________________________________________
> kvmarm mailing list
> kvmarm at lists.cs.columbia.edu
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm