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

Alexander Graf
2013-07-15T11:31:40Z

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
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html