Re: [PATCH v10 2/3] KVM: s390: guest support for topology function

[Pierre Morel]

On 6/24/22 11:32, Claudio Imbrenda wrote:
> On Mon, 20 Jun 2022 14:54:36 +0200
> Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
>
> > We report a topology change to the guest for any CPU hotplug.
> >
> > The reporting to the guest is done using the Multiprocessor
> > Topology-Change-Report (MTCR) bit of the utility entry in the guest's
> > SCA which will be cleared during the interpretation of PTF.
> >
> > On every vCPU creation we set the MCTR bit to let the guest know the
> > next time he uses the PTF with command 2 instruction that the
> > topology changed and that he should use the STSI(15.1.x) instruction
> > to get the topology details.
> >
> > STSI(15.1.x) gives information on the CPU configuration topology.
> > Let's accept the interception of STSI with the function code 15 and
> > let the userland part of the hypervisor handle it when userland
> > support the CPU Topology facility.
> >
> > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> > ---
> >   arch/s390/include/asm/kvm_host.h | 11 ++++++++---
> >   arch/s390/kvm/kvm-s390.c         | 27 ++++++++++++++++++++++++++-
> >   arch/s390/kvm/priv.c             | 15 +++++++++++----
> >   arch/s390/kvm/vsie.c             |  3 +++
> >   4 files changed, 48 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> > index 766028d54a3e..bb54196d4ed6 100644
> > --- a/arch/s390/include/asm/kvm_host.h
> > +++ b/arch/s390/include/asm/kvm_host.h
> > @@ -97,15 +97,19 @@ struct bsca_block {
> >   	union ipte_control ipte_control;
> >   	__u64	reserved[5];
> >   	__u64	mcn;
> > -	__u64	reserved2;
> > +#define SCA_UTILITY_MTCR	0x8000
> > +	__u16	utility;
> > +	__u8	reserved2[6];
> >   	struct bsca_entry cpu[KVM_S390_BSCA_CPU_SLOTS];
> >   };
> >   
> >   struct esca_block {
> >   	union ipte_control ipte_control;
> > -	__u64   reserved1[7];
> > +	__u64   reserved1[6];
> > +	__u16	utility;
> > +	__u8	reserved2[6];
> >   	__u64   mcn[4];
> > -	__u64   reserved2[20];
> > +	__u64   reserved3[20];
> >   	struct esca_entry cpu[KVM_S390_ESCA_CPU_SLOTS];
> >   };
> >   
> > @@ -249,6 +253,7 @@ struct kvm_s390_sie_block {
> >   #define ECB_SPECI	0x08
> >   #define ECB_SRSI	0x04
> >   #define ECB_HOSTPROTINT	0x02
> > +#define ECB_PTF		0x01
> >   	__u8	ecb;			/* 0x0061 */
> >   #define ECB2_CMMA	0x80
> >   #define ECB2_IEP	0x20
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index 8fcb56141689..95b96019ca8e 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -1691,6 +1691,25 @@ static int kvm_s390_get_cpu_model(struct kvm *kvm, struct kvm_device_attr *attr)
> >   	return ret;
> >   }
> >   
> > +/**
> > + * kvm_s390_sca_set_mtcr
>
> the format for kdoc is:
>
> 	function_name - very short description
>
> please add a very short description. something like:
>
> 	kvm_s390_sca_set_mtcr - update mtcr to signal topology change


OK, thanks,

Pierre

--
Pierre Morel
IBM Lab Boeblingen