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

Pierre Morel
2022-06-27T17:36:08Z

On 6/24/22 11:32, Claudio Imbrenda wrote:
> On Mon, 20 Jun 2022 14:54:36 +0200
> Pierre Morel <pmorel@linux.ibm.com> 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@linux.ibm.com>
>> ---
>> 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