Received-SPF: pass (google.com: domain of linux-kernel+bounces-174170-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Precedence: bulk
Mime-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset=UTF-8
Date: Thu, 09 May 2024 15:42:46 +1000
Message-Id: <D14VHEQLAB3V.30DDBZFDKZVGY@gmail.com>
Cc: <linuxppc-dev@lists.ozlabs.org>, <kvm@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, "Vaibhav Jain" <vaibhav@linux.ibm.com>
Subject: Re: [PATCH v6] arch/powerpc/kvm: Add support for reading VPA
 counters for pseries guests
From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Michael Ellerman" <mpe@ellerman.id.au>, "Gautam Menghani"
 <gautam@linux.ibm.com>, <christophe.leroy@csgroup.eu>,
 <naveen.n.rao@linux.ibm.com>
References: <20240506145605.73794-1-gautam@linux.ibm.com>
 <87o79gmqek.fsf@mail.lhotse>
In-Reply-To: <87o79gmqek.fsf@mail.lhotse>

On Wed May 8, 2024 at 10:36 PM AEST, Michael Ellerman wrote:
> Gautam Menghani <gautam@linux.ibm.com> writes:
> > PAPR hypervisor has introduced three new counters in the VPA area of
> > LPAR CPUs for KVM L2 guest (see [1] for terminology) observability - 2
> > for context switches from host to guest and vice versa, and 1 counter
> > for getting the total time spent inside the KVM guest. Add a tracepoint
> > that enables reading the counters for use by ftrace/perf. Note that thi=
s
> > tracepoint is only available for nestedv2 API (i.e, KVM on PowerVM).
> ...
> > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.=
c
> > index 8e86eb577eb8..ed69ad58bd02 100644
> > --- a/arch/powerpc/kvm/book3s_hv.c
> > +++ b/arch/powerpc/kvm/book3s_hv.c
> > @@ -4108,6 +4108,54 @@ static void vcpu_vpa_increment_dispatch(struct k=
vm_vcpu *vcpu)
> >  	}
> >  }
> > =20
> > +static inline int kvmhv_get_l2_counters_status(void)
> > +{
> > +	return get_lppaca()->l2_counters_enable;
> > +}
>
> This is breaking the powernv build:

[...]

All the nested KVM code should really go under CONFIG_PSERIES.
Possibly even moved out to its own file.

For now maybe you could just ifdef these few functions and
replace with noop variants for !PSERIES.

Thanks,
Nick