Re: [PATCH v10 25/26] KVM: s390: CPU model support for AP virtualization

Tony Krowiak
2018-09-21T23:31:07Z

On 09/12/2018 03:43 PM, Tony Krowiak wrote:
> From: Tony Krowiak <akrowiak@linux.ibm.com>
>
> 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.
>
> If this facility is not set for the KVM guest, then only
> APQNs with an APQI less than 16 will be used by a Linux
> guest regardless of the matrix configuration for the virtual
> machine. This is a limitation of the Linux AP bus.
>
> 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.
>
> 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 for the virtual
> machine. This is a limitation of the Linux AP bus.
>
> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Tested-by: Michael Mueller <mimu@linux.ibm.com>
> Tested-by: Farhan Ali <alifm@linux.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> arch/s390/kvm/kvm-s390.c | 5 +++++
> arch/s390/tools/gen_facilities.c | 2 ++
> 2 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 286c2e0..f0b8e2a 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -371,6 +371,11 @@ static void kvm_s390_cpu_feat_init(void)
>
> if (MACHINE_HAS_ESOP)
> allow_cpu_feat(KVM_S390_VM_CPU_FEAT_ESOP);
> +
> + /* Check if AP instructions installed on host */
> + if (ap_instructions_available())
> + allow_cpu_feat(KVM_S390_VM_CPU_FEAT_AP);
> +
> /*
> * We need SIE support, ESOP (PROT_READ protection for gmap_shadow),
> * 64bit SCAO (SCA passthrough) and IDTE (for gmap_shadow unshadowing).
> diff --git a/arch/s390/tools/gen_facilities.c b/arch/s390/tools/gen_facilities.c
> index 0c85aed..fd788e0 100644
> --- a/arch/s390/tools/gen_facilities.c
> +++ b/arch/s390/tools/gen_facilities.c
> @@ -106,6 +106,8 @@ struct facility_def {
>
> .name = "FACILITIES_KVM_CPUMODEL",
> .bits = (int[]){
> + 12, /* AP Query Configuration Information */
> + 15, /* AP Facilities Test */
> 156, /* etoken facility */
> -1 /* END */
> }
>

The fixup! patch below modifies this patch (25/26) to illustrate how
David's recommendation will be implemented for v11 of the series. It
is one of three fixup! patches (the other two are in responses to
03/26 and 11/26) included to generate discussion in v10 rather than
waiting until v11 for comments.

-----------------------------------8<-----------------------------------

From: Tony Krowiak <akrowiak@linux.ibm.com>
Date: Thu, 20 Sep 2018 13:28:07 -0400
Subject: [FIXUP v10] fixup!: KVM: s390: CPU model support for AP
virtualization

---
arch/s390/kvm/kvm-s390.c | 4 ----
1 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index a3a7cd9..ff38251 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -372,10 +372,6 @@ static void kvm_s390_cpu_feat_init(void)
if (MACHINE_HAS_ESOP)
allow_cpu_feat(KVM_S390_VM_CPU_FEAT_ESOP);

- /* Check if AP instructions installed on host */
- if (ap_instructions_available())
- allow_cpu_feat(KVM_S390_VM_CPU_FEAT_AP);
-
/*
* We need SIE support, ESOP (PROT_READ protection for gmap_shadow),
* 64bit SCAO (SCA passthrough) and IDTE (for gmap_shadow unshadowing).
--
1.7.1