Re: [PATCH v2 04/10] KVM: arm: guest debug, add stub KVM_SET_GUEST_DEBUG ioctl

Alex Bennée
2015-04-09T14:19:07Z

Andrew Jones <drjones@redhat.com> writes:

> On Wed, Apr 01, 2015 at 05:55:29PM +0200, David Hildenbrand wrote:
>> > This commit adds a stub function to support the KVM_SET_GUEST_DEBUG
>> > ioctl. Currently any operation flag will return EINVAL. Actual
>>
>> Well it won't return -EINVAL if you push in KVM_GUESTDBG_ENABLE or 0.
>>
>> "Any unsupported flag will return -EINVAL. For now, only KVM_GUESTDBG_ENABLE is
>> supported, although it won't have any effects."
>>
>> > functionality will be added with further patches.
>> >
>> > Signed-off-by: Alex Bennée <alex.bennee@linaro.org>.
>> >
>> > ---
>> > v2
>> > - simplified form of the ioctl (stuff will go into setup_debug)
>> >
>> > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
>> > index b112efc..06c5064 100644
>> > --- a/Documentation/virtual/kvm/api.txt
>> > +++ b/Documentation/virtual/kvm/api.txt
>> > @@ -2604,7 +2604,7 @@ 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 5560f74..445933d 100644
>> > --- a/arch/arm/kvm/arm.c
>> > +++ b/arch/arm/kvm/arm.c
>> > @@ -183,6 +183,7 @@ 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:
>> > r = 1;
>> > break;
>> > case KVM_CAP_COALESCED_MMIO:
>> > @@ -303,10 +304,21 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>> > kvm_arm_set_running_vcpu(NULL);
>> > }
>> >
>> > +#define KVM_GUESTDBG_VALID (KVM_GUESTDBG_ENABLE)
>>
>> That makes me rather think that it is another flag.
>>
>> We(s390x) use VALID_GUESTDBG_FLAGS, what about that or KVM_GUESTDBG_VALID_MASK?
>>
>> > +
>> > int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
>> > struct kvm_guest_debug *dbg)
>> > {
>> > - return -EINVAL;
>> > + if (dbg->control & KVM_GUESTDBG_ENABLE) {
>> > + if (dbg->control & ~KVM_GUESTDBG_VALID)
>> > + return -EINVAL;
>>
>> I'd move that check directly to the start of the function and bail out on any
>> unsupported flag.
>>
>> > +
>> > + vcpu->guest_debug = dbg->control;
>> > + } else {
>> > + /* If not enabled clear all flags */
>> > + vcpu->guest_debug = 0;
>> > + }
>> > + return 0;
>> > }
>> >
>> >
>>
>> David
>>
>
> I don't see any follow-up from Alex on this, so I feel the need to
> "+1" all David's comments here.

Yeah they make sense. Will do.

--
Alex Bennée