| Message ID | 20201204054415.579042-14-david@gibson.dropbear.id.au (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Generalize memory encryption models | expand |
On Fri, 4 Dec 2020 16:44:15 +1100 David Gibson <david@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 "securable-guest-memory" machine s/bythe/by the/ > 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 securable-guest-memory 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 securable-guest-memory is set, we will > either create a guest capable of entering PV mode, or fail outright s/outright/outright./ > > - If securable-guest-memory is not set, guest's might still be able to s/guest's/guests/ > enter PV mode, if the CPU has the right model. This may be a > little surprising, but shouldn't actually be harmful. > > To start a guest supporting Protected Virtualization using the new > option use the command line arguments: > -object s390-pv-guest,id=pv0 -machine securable-guest-memory=pv0 > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > --- > hw/s390x/pv.c | 58 +++++++++++++++++++++++++++++++++++++++++++ > include/hw/s390x/pv.h | 1 + > target/s390x/kvm.c | 3 +++ > 3 files changed, 62 insertions(+) > Modulo any naming changes etc., I think this should work for s390. I don't have the hardware to test this, however, and would appreciate someone with a PV setup giving this a go.
On Tue, Dec 15, 2020 at 12:45:26PM +0100, Cornelia Huck wrote: > On Fri, 4 Dec 2020 16:44:15 +1100 > David Gibson <david@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 "securable-guest-memory" machine > > s/bythe/by the/ > > > 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 securable-guest-memory 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 securable-guest-memory is set, we will > > either create a guest capable of entering PV mode, or fail outright > > s/outright/outright./ > > > > > - If securable-guest-memory is not set, guest's might still be able to > > s/guest's/guests/ All those corrected, thanks. > > enter PV mode, if the CPU has the right model. This may be a > > little surprising, but shouldn't actually be harmful. > > > > To start a guest supporting Protected Virtualization using the new > > option use the command line arguments: > > -object s390-pv-guest,id=pv0 -machine securable-guest-memory=pv0 > > > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > > --- > > hw/s390x/pv.c | 58 +++++++++++++++++++++++++++++++++++++++++++ > > include/hw/s390x/pv.h | 1 + > > target/s390x/kvm.c | 3 +++ > > 3 files changed, 62 insertions(+) > > > > Modulo any naming changes etc., I think this should work for s390. I > don't have the hardware to test this, however, and would appreciate > someone with a PV setup giving this a go. Makes sense.
diff --git a/hw/s390x/pv.c b/hw/s390x/pv.c index ab3a2482aa..9fddc196a3 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/securable-guest-memory.h" #include "hw/s390x/ipl.h" #include "hw/s390x/pv.h" @@ -111,3 +114,58 @@ 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 + * securable guest memory system to use s390's PV mechanism. + * + * # $QEMU \ + * -object s390-pv-guest,id=pv0 \ + * -machine ...,securable-guest-memory=pv0 + */ +struct S390PVGuestState { + Object parent_obj; +}; + +int s390_pv_init(SecurableGuestMemory *sgm, Error **errp) +{ + if (!object_dynamic_cast(OBJECT(sgm), TYPE_S390_PV_GUEST)) { + return 0; + } + + if (!s390_has_feat(S390_FEAT_UNPACK)) { + error_setg(errp, + "CPU model does not support Protected Virtualization"); + return -1; + } + + sgm->ready = true; + + return 0; +} + +static const TypeInfo s390_pv_guest_info = { + .parent = TYPE_SECURABLE_GUEST_MEMORY, + .name = TYPE_S390_PV_GUEST, + .instance_size = sizeof(S390PVGuestState), + .interfaces = (InterfaceInfo[]) { + { TYPE_USER_CREATABLE }, + { } + } +}; + +static void +s390_pv_register_types(void) +{ + type_register_static(&s390_pv_guest_info); +} + +type_init(s390_pv_register_types); diff --git a/include/hw/s390x/pv.h b/include/hw/s390x/pv.h index aee758bc2d..4250af699b 100644 --- a/include/hw/s390x/pv.h +++ b/include/hw/s390x/pv.h @@ -43,6 +43,7 @@ void s390_pv_prep_reset(void); int s390_pv_verify(void); void s390_pv_unshare(void); void s390_pv_inject_reset_error(CPUState *cs); +int s390_pv_init(SecurableGuestMemory *sgm, Error **errp); #else /* CONFIG_KVM */ static inline bool s390_is_pv(void) { return false; } static inline int s390_pv_vm_enable(void) { return 0; } diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c index b8385e6b95..3383487463 100644 --- a/target/s390x/kvm.c +++ b/target/s390x/kvm.c @@ -387,6 +387,9 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES); + + s390_pv_init(ms->sgm, &error_fatal); + return 0; }
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 "securable-guest-memory" 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 securable-guest-memory 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 securable-guest-memory is set, we will either create a guest capable of entering PV mode, or fail outright - If securable-guest-memory 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. To start a guest supporting Protected Virtualization using the new option use the command line arguments: -object s390-pv-guest,id=pv0 -machine securable-guest-memory=pv0 Signed-off-by: David Gibson <david@gibson.dropbear.id.au> --- hw/s390x/pv.c | 58 +++++++++++++++++++++++++++++++++++++++++++ include/hw/s390x/pv.h | 1 + target/s390x/kvm.c | 3 +++ 3 files changed, 62 insertions(+)