Messages in this thread | | | Subject | Re: [PATCH v6 05/21] KVM: s390: CPU model support for AP virtualization | From | Halil Pasic <> | Date | Mon, 2 Jul 2018 18:20:55 +0200 |
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On 07/02/2018 06:11 PM, Cornelia Huck wrote: > On Mon, 2 Jul 2018 11:54:28 -0400 > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > >> On 07/02/2018 11:41 AM, Cornelia Huck wrote: >>> On Mon, 2 Jul 2018 11:37:11 -0400 >>> Tony Krowiak <akrowiak@linux.ibm.com> wrote: >>> >>>> On 07/02/2018 10:38 AM, Christian Borntraeger wrote: >>>>> On 06/29/2018 11:11 PM, Tony Krowiak wrote: >>>>>> Introduces a new CPU model feature and two CPU model >>>>>> facilities to support AP virtualization for KVM guests. >>>>>> >>>>>> CPU model feature: >>>>>> >>>>>> The KVM_S390_VM_CPU_FEAT_AP feature indicates that >>>>>> AP instructions are available on the guest. This >>>>>> feature will be enabled by the kernel only if the AP >>>>>> instructions are installed on the linux host. This feature >>>>>> must be specifically turned on for the KVM guest from >>>>>> userspace to use the VFIO AP device driver for guest >>>>>> access to AP devices. >>>>>> >>>>>> CPU model facilities: >>>>>> >>>>>> 1. AP Query Configuration Information (QCI) facility is installed. >>>>>> >>>>>> This is indicated by setting facilities bit 12 for >>>>>> the guest. The kernel will not enable this facility >>>>>> for the guest if it is not set on the host. This facility >>>>>> must not be set by userspace if the KVM_S390_VM_CPU_FEAT_AP >>>>>> feature is not installed. >>>>>> >>>>>> If this facility is not set for the KVM guest, then only >>>>>> APQNs with an APQI less than 16 will be available to the >>>>>> guest regardless of the guest's matrix configuration. This >>>>>> is a limitation of the AP bus running on the guest. >>>>>> >>>>>> 2. AP Facilities Test facility (APFT) is installed. >>>>>> >>>>>> This is indicated by setting facilities bit 15 for >>>>>> the guest. The kernel will not enable this facility for >>>>>> the guest if it is not set on the host. This facility >>>>>> must not be set by userspace if the KVM_S390_VM_CPU_FEAT_AP >>>>>> feature is not installed. >>>>>> >>>>>> If this facility is not set for the KVM guest, then no >>>>>> AP devices will be available to the guest regardless of >>>>>> the guest's matrix configuration. This is a limitation >>>>>> of the AP bus running under the guest. >>>>>> >>>>>> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> >>>>>> Reviewed-by: Halil Pasic <pasic@linux.ibm.com> >>>>>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> >>>>> I think it probably should be at the end of the series, other than that its good. >>>> If I move this to the end of the series, the very next patch checks the >>>> >>>> KVM_S390_VM_CPU_FEAT_AP feature? >>> Introduce it here, offer it only with the last patch? >> >> I apologize, but I don't know what you mean by this. Are you suggesting >> this patch >> should only include the #define for KVM_S390_VM_CPU_FEAT_AP? > > Yes, just introduce the definition here (so code later in the series > can refer to it) and flip the switch (offer the bit) as the final > patch. >
The other features introduced and exposed here are no different. For KVM_S390_VM_CPU_FEAT_AP defer exposing means defer allow_cpu_feat(); for the STFLE features, defer adding to FACILITIES_KVM_CPUMODEL.
Anyway, I think the definition should be squashed into #6. Expose the features after patch #6 is in place or expose them at the end of the series is IMHO a matter of taste -- and I lean towards expose at the end of the series.
Regards, Halil
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