Re: [PATCH 2/5] booke: exit to guest userspace for unimplemented hcalls in kvm

[Alexander Graf <agraf@suse.de>]

On 15.07.2013, at 13:11, Bharat Bhushan wrote:

> Exit to guest user space if kvm does not implement the hcall.
> 
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> ---
> arch/powerpc/kvm/booke.c   |   47 +++++++++++++++++++++++++++++++++++++------
> arch/powerpc/kvm/powerpc.c |    1 +
> include/uapi/linux/kvm.h   |    1 +
> 3 files changed, 42 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 17722d8..c8b41b4 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -1005,9 +1005,25 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> 		break;
> 
> #ifdef CONFIG_KVM_BOOKE_HV
> -	case BOOKE_INTERRUPT_HV_SYSCALL:
> +	case BOOKE_INTERRUPT_HV_SYSCALL: {

This is getting large. Please extract hcall handling into its own function. Maybe you can merge the HV and non-HV case then too.

> +		int i;
> 		if (!(vcpu->arch.shared->msr & MSR_PR)) {
> -			kvmppc_set_gpr(vcpu, 3, kvmppc_kvm_pv(vcpu));
> +			r = kvmppc_kvm_pv(vcpu);
> +			if (r != EV_UNIMPLEMENTED) {
> +				/* except unimplemented return to guest */
> +				kvmppc_set_gpr(vcpu, 3, r);
> +				kvmppc_account_exit(vcpu, SYSCALL_EXITS);
> +				r = RESUME_GUEST;
> +				break;
> +			}
> +			/* Exit to userspace for unimplemented hcalls in kvm */
> +			run->epapr_hcall.nr = kvmppc_get_gpr(vcpu, 11);
> +			run->epapr_hcall.ret = 0;
> +			for (i = 0; i < 8; i++)
> +				run->epapr_hcall.args[i] = kvmppc_get_gpr(vcpu, 3 + i);
> +			vcpu->arch.hcall_needed = 1;
> +			kvmppc_account_exit(vcpu, SYSCALL_EXITS);
> +			r = RESUME_HOST;
> 		} else {
> 			/*
> 			 * hcall from guest userspace -- send privileged
> @@ -1016,22 +1032,39 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
> 			kvmppc_core_queue_program(vcpu, ESR_PPR);
> 		}
> 
> -		r = RESUME_GUEST;
> +		run->exit_reason = KVM_EXIT_EPAPR_HCALL;

This looks odd. Your exit reason only changes when you do the hcall exiting, right?

You also need to guard user space hcall exits with an ENABLE_CAP. Otherwise older user space will break, as it doesn't know about the exit type yet.


Alex

> 		break;
> +	}
> #else
> -	case BOOKE_INTERRUPT_SYSCALL:
> +	case BOOKE_INTERRUPT_SYSCALL: {
> +		int i;
> +		r = RESUME_GUEST;
> 		if (!(vcpu->arch.shared->msr & MSR_PR) &&
> 		    (((u32)kvmppc_get_gpr(vcpu, 0)) = KVM_SC_MAGIC_R0)) {
> 			/* KVM PV hypercalls */
> -			kvmppc_set_gpr(vcpu, 3, kvmppc_kvm_pv(vcpu));
> -			r = RESUME_GUEST;
> +			r = kvmppc_kvm_pv(vcpu);
> +			if (r != EV_UNIMPLEMENTED) {
> +				/* except unimplemented return to guest */
> +				kvmppc_set_gpr(vcpu, 3, r);
> +				kvmppc_account_exit(vcpu, SYSCALL_EXITS);
> +				r = RESUME_GUEST;
> +				break;
> +			}
> +			/* Exit to userspace for unimplemented hcalls in kvm */
> +			run->epapr_hcall.nr = kvmppc_get_gpr(vcpu, 11);
> +			run->epapr_hcall.ret = 0;
> +			for (i = 0; i < 8; i++)
> +				run->epapr_hcall.args[i] = kvmppc_get_gpr(vcpu, 3 + i);
> +			vcpu->arch.hcall_needed = 1;
> +			run->exit_reason = KVM_EXIT_EPAPR_HCALL;
> +			r = RESUME_HOST;
> 		} else {
> 			/* Guest syscalls */
> 			kvmppc_booke_queue_irqprio(vcpu, BOOKE_IRQPRIO_SYSCALL);
> 		}
> 		kvmppc_account_exit(vcpu, SYSCALL_EXITS);
> -		r = RESUME_GUEST;
> 		break;
> +	}
> #endif
> 
> 	case BOOKE_INTERRUPT_DTLB_MISS: {
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 4e05f8c..6c6199d 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -307,6 +307,7 @@ int kvm_dev_ioctl_check_extension(long ext)
> 	case KVM_CAP_PPC_BOOKE_SREGS:
> 	case KVM_CAP_PPC_BOOKE_WATCHDOG:
> 	case KVM_CAP_PPC_EPR:
> +	case KVM_CAP_EXIT_EPAPR_HCALL:
> #else
> 	case KVM_CAP_PPC_SEGSTATE:
> 	case KVM_CAP_PPC_HIOR:
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 01ee50e..b5266e5 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -674,6 +674,7 @@ struct kvm_ppc_smmu_info {
> #define KVM_CAP_PPC_RTAS 91
> #define KVM_CAP_IRQ_XICS 92
> #define KVM_CAP_ARM_EL1_32BIT 93
> +#define KVM_CAP_EXIT_EPAPR_HCALL 94
> 
> #ifdef KVM_CAP_IRQ_ROUTING
> 
> -- 
> 1.7.0.4
> 
> 
> --
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