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

    drew


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