On 7/27/20 5:50 PM, Cornelia Huck wrote: > On Fri, 24 Jul 2020 12:57:44 +1000 > David Gibson <da...@gibson.dropbear.id.au> wrote: > >> At least some s390 cpu models support "Protected Virtualization" (PV), >> a mechanism to protect guests from eavesdropping by a compromised >> hypervisor. >> >> This is similar in function to other mechanisms like AMD's SEV and >> POWER's PEF, which are controlled bythe "host-trust-limitation" >> machine option. s390 is a slightly special case, because we already >> supported PV, simply by using a CPU model with the required feature >> (S390_FEAT_UNPACK). >> >> To integrate this with the option used by other platforms, we >> implement the following compromise: >> >> - When the host-trust-limitation option is set, s390 will recognize >> it, verify that the CPU can support PV (failing if not) and set >> virtio default options necessary for encrypted or protected guests, >> as on other platforms. i.e. if host-trust-limitation is set, we >> will either create a guest capable of entering PV mode, or fail >> outright >> >> - If host-trust-limitation is not set, guest's might still be able to >> enter PV mode, if the CPU has the right model. This may be a >> little surprising, but shouldn't actually be harmful. > > This could be workable, I guess. Would like a second opinion, though. > >> >> To start a guest supporting Protected Virtualization using the new >> option use the command line arguments: >> -object s390-pv-guest,id=pv0 -machine host-trust-limitation=pv0 >> >> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> >> --- >> hw/s390x/pv.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++ >> 1 file changed, 61 insertions(+) >> >> diff --git a/hw/s390x/pv.c b/hw/s390x/pv.c >> index ab3a2482aa..4bf3b345b6 100644 >> --- a/hw/s390x/pv.c >> +++ b/hw/s390x/pv.c >> @@ -14,8 +14,11 @@ >> #include <linux/kvm.h> >> >> #include "cpu.h" >> +#include "qapi/error.h" >> #include "qemu/error-report.h" >> #include "sysemu/kvm.h" >> +#include "qom/object_interfaces.h" >> +#include "exec/host-trust-limitation.h" >> #include "hw/s390x/ipl.h" >> #include "hw/s390x/pv.h" >> >> @@ -111,3 +114,61 @@ void s390_pv_inject_reset_error(CPUState *cs) >> /* Report that we are unable to enter protected mode */ >> env->regs[r1 + 1] = DIAG_308_RC_INVAL_FOR_PV; >> } >> + >> +#define TYPE_S390_PV_GUEST "s390-pv-guest" >> +#define S390_PV_GUEST(obj) \ >> + OBJECT_CHECK(S390PVGuestState, (obj), TYPE_S390_PV_GUEST) >> + >> +typedef struct S390PVGuestState S390PVGuestState; >> + >> +/** >> + * S390PVGuestState: >> + * >> + * The S390PVGuestState object is basically a dummy used to tell the >> + * host trust limitation system to use s390's PV mechanism. guest. >> + * >> + * # $QEMU \ >> + * -object s390-pv-guest,id=pv0 \ >> + * -machine ...,host-trust-limitation=pv0 >> + */ >> +struct S390PVGuestState { >> + Object parent_obj; >> +}; >> + >> +static int s390_pv_kvm_init(HostTrustLimitation *gmpo, Error **errp) >> +{ >> + if (!s390_has_feat(S390_FEAT_UNPACK)) { >> + error_setg(errp, >> + "CPU model does not support Protected Virtualization"); >> + return -1; >> + } >> + >> + return 0; >> +} > > So here's where I'm confused: If I follow the code correctly, the > ->kvm_init callback is invoked before kvm_arch_init() is called. The > kvm_arch_init() implementation for s390x checks whether > KVM_CAP_S390_PROTECTED is available, which is a pre-req for > S390_FEAT_UNPACK. Am I missing something? Can someone with access to PV > hardware check whether this works as intended?
Doesn't look good: ./s390x-run s390x/stsi.img -object s390-pv-guest,id=pv0 -machine host-trust-limitation=pv0 /usr/local/bin/qemu-system-s390x -nodefaults -nographic -machine s390-ccw-virtio,accel=kvm -chardev stdio,id=con0 -device sclpconsole,chardev=con0 -kernel s390x/stsi.img -object s390-pv-guest,id=pv0 -machine host-trust-limitation=pv0 # -initrd /tmp/tmp.uacr85fJnw qemu-system-s390x: CPU model does not support Protected Virtualization qemu-system-s390x: failed to initialize kvm: Operation not permitted Without the htl it's happy. > >> + >> +static void s390_pv_guest_class_init(ObjectClass *oc, void *data) >> +{ >> + HostTrustLimitationClass *gmpc = HOST_TRUST_LIMITATION_CLASS(oc); >> + >> + gmpc->kvm_init = s390_pv_kvm_init; >> +} >> + >> +static const TypeInfo s390_pv_guest_info = { >> + .parent = TYPE_OBJECT, >> + .name = TYPE_S390_PV_GUEST, >> + .instance_size = sizeof(S390PVGuestState), >> + .class_init = s390_pv_guest_class_init, >> + .interfaces = (InterfaceInfo[]) { >> + { TYPE_HOST_TRUST_LIMITATION }, >> + { TYPE_USER_CREATABLE }, >> + { } >> + } >> +}; >> + >> +static void >> +s390_pv_register_types(void) >> +{ >> + type_register_static(&s390_pv_guest_info); >> +} >> + >> +type_init(s390_pv_register_types); >
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