On 27/03/2018 12:59, Cornelia Huck wrote:
On Wed, 14 Mar 2018 14:25:43 -0400
Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> 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.
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.
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx>
---
arch/s390/include/asm/kvm_host.h | 1 +
arch/s390/include/uapi/asm/kvm.h | 1 +
arch/s390/kvm/kvm-s390.c | 4 ++++
arch/s390/tools/gen_facilities.c | 2 ++
4 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index c47731d..a60c45b 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -350,6 +350,10 @@ static void kvm_s390_cpu_feat_init(void)
if (MACHINE_HAS_ESOP)
allow_cpu_feat(KVM_S390_VM_CPU_FEAT_ESOP);
+
+ if (ap_instructions_installed()) /* AP instructions installed on host */
+ allow_cpu_feat(KVM_S390_VM_CPU_FEAT_AP);
That's another dependency of the base kvm-s390 module on zcrypt, which
I don't like at all.
In fact there is a tricky thing about zcrypt it is that even it is
configured a a module
CONFIG_ZCRYPT=M, the AP BUS is built statically with the kernel.
See drivers/s390/crypto/Makefile
"
ap-objs := ap_bus.o ap_card.o ap_queue.o
obj-$(subst m,y,$(CONFIG_ZCRYPT)) += ap.o
"
ugly isn't it?
There are two possibilities here:
- Exposing the features makes sense even if no zcrypt driver is active
in the host. Then, ap_instructions_installed() needs to be moved into
always-built code (see my comments for the interface in patch 1).
This is what we need for future enhancement I think.
- Exposing the features makes sense only if we actually want to make
vfio-ap available. Then we should provide the proper check in the
vfio-ap parts (which depends on zcrypt) and stub it out if vfio-ap is
not configured.
+
/*
* We need SIE support, ESOP (PROT_READ protection for gmap_shadow),
* 64bit SCAO (SCA passthrough) and IDTE (for gmap_shadow unshadowing).
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
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