Messages in this thread | | | Subject | Re: [PATCH v3 03/14] KVM: s390: CPU model support for AP virtualization | From | Pierre Morel <> | Date | Tue, 27 Mar 2018 13:22:56 +0200 |
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On 27/03/2018 12:59, Cornelia Huck wrote: > On Wed, 14 Mar 2018 14:25:43 -0400 > Tony Krowiak <akrowiak@linux.vnet.ibm.com> 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@de.ibm.com> >> Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com> >> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com> >> --- >> 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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