Re: [PATCH 3/7] KVM: arm: guest debug, add stub KVM_SET_GUEST_DEBUG ioctl

From: Christoffer Dall
Date: Sat Nov 29 2014 - 11:20:33 EST


On Tue, Nov 25, 2014 at 04:10:01PM +0000, Alex Bennée wrote:
> This commit adds a stub function to support the KVM_SET_GUEST_DEBUG
> ioctl. Currently any operation flag will return EINVAL. Actual
> functionality will be added with further patches.
>
> Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx>.
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 7610eaa..2c6386e 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2570,7 +2570,7 @@ handled.
> 4.87 KVM_SET_GUEST_DEBUG
>
> Capability: KVM_CAP_SET_GUEST_DEBUG
> -Architectures: x86, s390, ppc
> +Architectures: x86, s390, ppc, arm64
> Type: vcpu ioctl
> Parameters: struct kvm_guest_debug (in)
> Returns: 0 on success; -1 on error
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 9e193c8..a0ff410 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -180,6 +180,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_ARM_PSCI:
> case KVM_CAP_ARM_PSCI_0_2:
> case KVM_CAP_READONLY_MEM:
> + case KVM_CAP_SET_GUEST_DEBUG:

Don't we usually wait with introducing visibility to user space until
you actually do support the ioctl?

> r = 1;
> break;
> case KVM_CAP_COALESCED_MMIO:
> @@ -302,7 +303,34 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> struct kvm_guest_debug *dbg)
> {
> - return -EINVAL;
> + /* If it's not enabled clear all flags */
> + if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
> + vcpu->guest_debug = 0;
> + return 0;
> + }
> +
> + vcpu->guest_debug = dbg->control;
> + kvm_info("%s: guest_debug is 0x%lx\n", __func__, vcpu->guest_debug);
> +
> + /* Single Step */
> + if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> + kvm_info("SS requested, not yet implemented\n");
> + return -EINVAL;
> + }
> +
> + /* Software Break Points */
> + if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) {
> + kvm_info("SW BP support requested, not yet implemented\n");
> + return -EINVAL;
> + }
> +
> + /* Hardware assisted Break and Watch points */
> + if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) {
> + kvm_info("HW BP support requested, not yet implemented\n");
> + return -EINVAL;
> + }
> +
> + return 0;
> }
>
>
> --
> 2.1.3
>
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