From: Paul Mackerras <paulus@ozlabs.org>
To: Fabiano Rosas <farosas@linux.ibm.com>
Cc: kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
kvm@vger.kernel.org, benh@kernel.crashing.org,
mpe@ellerman.id.au, pbonzini@redhat.com, rkrcmar@redhat.com,
david@gibson.dropbear.id.au, aik@ozlabs.ru
Subject: Re: [PATCH v2] KVM: PPC: Report single stepping capability
Date: Mon, 17 Jun 2019 16:16:08 +1000 [thread overview]
Message-ID: <20190617061608.y5qw26i53si76qqt@oak.ozlabs.ibm.com> (raw)
In-Reply-To: <20190529222219.27994-1-farosas@linux.ibm.com>
On Wed, May 29, 2019 at 07:22:19PM -0300, Fabiano Rosas wrote:
> When calling the KVM_SET_GUEST_DEBUG ioctl, userspace might request
> the next instruction to be single stepped via the
> KVM_GUESTDBG_SINGLESTEP control bit of the kvm_guest_debug structure.
>
> We currently don't have support for guest single stepping implemented
> in Book3S HV.
>
> This patch adds the KVM_CAP_PPC_GUEST_DEBUG_SSTEP capability in order
> to inform userspace about the state of single stepping support.
Comment/question below:
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -538,6 +538,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> case KVM_CAP_IMMEDIATE_EXIT:
> r = 1;
> break;
> + case KVM_CAP_PPC_GUEST_DEBUG_SSTEP:
> +#ifdef CONFIG_BOOKE
> + r = 1;
> + break;
> +#endif
In the !CONFIG_BOOKE case, this will fall through to code which will
return 0 for HV KVM or 1 for PR KVM. Is that what was intended?
If so, then why do we need the CONFIG_BOOKE case? Isn't hv_enabled
always 0 on Book E?
In any case, I think this needs at least a /* fall through */ comment
in the code, and something explicit in the patch description to say
that we intend to return 1 on PR KVM.
Paul.
next prev parent reply other threads:[~2019-06-17 6:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-29 22:22 [PATCH v2] KVM: PPC: Report single stepping capability Fabiano Rosas
2019-06-17 6:16 ` Paul Mackerras [this message]
2019-06-17 19:25 ` Fabiano Rosas
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