On Tue, 27 Mar 2018 13:22:56 +0200 Pierre Morel <pmorel@xxxxxxxxxxxxxxxxxx> wrote: > 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? Yeah, I found it... interesting the first time I saw 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. OK, so that function needs to go into whatever place the interface used in patch 1 goes to as well. > > > - 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). > >
