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Subject[PATCH v8 21/22] KVM: s390: CPU model support for AP virtualization
Date
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. 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 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. 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 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>
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 | 7 +++++++
arch/s390/tools/gen_facilities.c | 2 ++
2 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 9203f0b..7d4fe9b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -367,6 +367,13 @@ 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() == 0)
+ 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 90a8c9e..a52290b 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 */
-1 /* END */
}
},
--
1.7.1
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