Subject: Re: [RFC PATCH 12/26] kvm: arm64: Add SMC handler in nVHE EL2

From: Marc Zyngier <[email-masked]>
Date: Thu, 05 Nov 2020 11:08:38 +0000

On 2020-11-04 18:36, David Brazdil wrote:
> Add handler of host SMCs in KVM nVHE trap handler. Forward all SMCs to
> EL3 and propagate the result back to EL1. This is done in preparation
> for validating host SMCs.
> 
> Signed-off-by: David Brazdil <[email-masked]>
> ---
>  arch/arm64/kvm/hyp/nvhe/hyp-main.c | 36 ++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index 19332c20fcde..fffc2dc09a1f 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -106,6 +106,38 @@ static void handle_host_hcall(struct
> kvm_cpu_context *host_ctxt)
>  	host_ctxt->regs.regs[1] = ret;
>  }
> 
> +static void skip_host_instruction(void)
> +{
> +	write_sysreg_el2(read_sysreg_el2(SYS_ELR) + 4, SYS_ELR);
> +}
> +
> +static void forward_host_smc(struct kvm_cpu_context *host_ctxt)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_smc(host_ctxt->regs.regs[0], host_ctxt->regs.regs[1],
> +			  host_ctxt->regs.regs[2], host_ctxt->regs.regs[3],
> +			  host_ctxt->regs.regs[4], host_ctxt->regs.regs[5],
> +			  host_ctxt->regs.regs[6], host_ctxt->regs.regs[7],
> +			  &res);
> +	host_ctxt->regs.regs[0] = res.a0;
> +	host_ctxt->regs.regs[1] = res.a1;
> +	host_ctxt->regs.regs[2] = res.a2;
> +	host_ctxt->regs.regs[3] = res.a3;
> +}
> +
> +static void handle_host_smc(struct kvm_cpu_context *host_ctxt)
> +{
> +	/*
> +	 * Unlike HVC, the return address of an SMC is the instruction's PC.
> +	 * Move the return address past the instruction.
> +	 */
> +	skip_host_instruction();
> +
> +	/* Forward SMC not handled in EL2 to EL3. */
> +	forward_host_smc(host_ctxt);
> +}
> +
>  void handle_trap(struct kvm_cpu_context *host_ctxt)
>  {
>  	u64 esr = read_sysreg_el2(SYS_ESR);
> @@ -114,6 +146,10 @@ void handle_trap(struct kvm_cpu_context 
> *host_ctxt)
>  	case ESR_ELx_EC_HVC64:
>  		handle_host_hcall(host_ctxt);
>  		break;
> +	case ESR_ELx_EC_SMC32:

How is that even possible? Host EL1 is strictly 64bit, so SMC32 cannot 
occur.

> +	case ESR_ELx_EC_SMC64:
> +		handle_host_smc(host_ctxt);
> +		break;
>  	default:
>  		hyp_panic();
>  	}

Thanks,

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

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