| Message ID | 20210113235811.1909610-14-david@gibson.dropbear.id.au (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Generalize memory encryption models | expand |
On 14.01.21 00:58, David Gibson wrote: [...] > +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) > +{ > + if (!object_dynamic_cast(OBJECT(cgs), 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; > + } I am triggering this and I guess this is because the cpu model is not yet initialized at this point in time.
On 14.01.21 10:10, Christian Borntraeger wrote: > > > On 14.01.21 00:58, David Gibson wrote: > [...] >> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) >> +{ >> + if (!object_dynamic_cast(OBJECT(cgs), 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; >> + } > > I am triggering this and I guess this is because the cpu model is not yet initialized at > this point in time. > When I remove the check, things seems to work though ( I can access virtio-blk devices without specifying iommu for example)
On 14.01.21 10:19, Christian Borntraeger wrote: > > > On 14.01.21 10:10, Christian Borntraeger wrote: >> >> >> On 14.01.21 00:58, David Gibson wrote: >> [...] >>> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) >>> +{ >>> + if (!object_dynamic_cast(OBJECT(cgs), 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; >>> + } >> >> I am triggering this and I guess this is because the cpu model is not yet initialized at >> this point in time. >> > When I remove the check, things seems to work though ( I can access virtio-blk devices without > specifying iommu for example) Maybe we can turn things around and check in apply_cpu_model if the object exists but unpack was not specified?
On Thu, Jan 14, 2021 at 10:10:02AM +0100, Christian Borntraeger wrote: > > > On 14.01.21 00:58, David Gibson wrote: > [...] > > +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) > > +{ > > + if (!object_dynamic_cast(OBJECT(cgs), 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; > > + } > > I am triggering this and I guess this is because the cpu model is not yet initialized at > this point in time. Bother. I thought I'd put the s390_pv_init() call late enough to avoid that, but I guess not. Any chance you can debug that? Working on s390 is far from easy for me.
On Thu, Jan 14, 2021 at 10:24:57AM +0100, Christian Borntraeger wrote: > > > On 14.01.21 10:19, Christian Borntraeger wrote: > > > > > > On 14.01.21 10:10, Christian Borntraeger wrote: > >> > >> > >> On 14.01.21 00:58, David Gibson wrote: > >> [...] > >>> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) > >>> +{ > >>> + if (!object_dynamic_cast(OBJECT(cgs), 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; > >>> + } > >> > >> I am triggering this and I guess this is because the cpu model is not yet initialized at > >> this point in time. > >> > > When I remove the check, things seems to work though ( I can access virtio-blk devices without > > specifying iommu for example) > > Maybe we can turn things around and check in apply_cpu_model if the object exists but > unpack was not specified? That might work. If unpack *is* specified, you'd also need to set the ready flag there, of course.
On Thu, 14 Jan 2021 10:58:11 +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 by the "confidential-guest-support" > 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 confidential-guest-support 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 confidential-guest-support > is set, we will either create a guest capable of entering PV mode, > or fail outright. > > - If confidential-guest-support is not set, guests 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 confidential-guest-support=pv0 > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > --- > docs/confidential-guest-support.txt | 3 ++ > docs/system/s390x/protvirt.rst | 19 ++++++--- > hw/s390x/pv.c | 62 +++++++++++++++++++++++++++++ > include/hw/s390x/pv.h | 1 + > target/s390x/kvm.c | 3 ++ > 5 files changed, 82 insertions(+), 6 deletions(-) > (...) > +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) > +{ > + if (!object_dynamic_cast(OBJECT(cgs), 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; > + } > + > + cgs->ready = true; > + > + return 0; > +} Do we want to add a migration blocker here? If we keep the one that is added when the guest transitions, we'll end up with two of them, but that might be easier than trying to unify it.
On 15.01.21 17:36, Cornelia Huck wrote: > On Thu, 14 Jan 2021 10:58:11 +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 by the "confidential-guest-support" >> 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 confidential-guest-support 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 confidential-guest-support >> is set, we will either create a guest capable of entering PV mode, >> or fail outright. >> >> - If confidential-guest-support is not set, guests 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 confidential-guest-support=pv0 >> >> Signed-off-by: David Gibson <david@gibson.dropbear.id.au> >> --- >> docs/confidential-guest-support.txt | 3 ++ >> docs/system/s390x/protvirt.rst | 19 ++++++--- >> hw/s390x/pv.c | 62 +++++++++++++++++++++++++++++ >> include/hw/s390x/pv.h | 1 + >> target/s390x/kvm.c | 3 ++ >> 5 files changed, 82 insertions(+), 6 deletions(-) >> > > (...) > >> +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) >> +{ >> + if (!object_dynamic_cast(OBJECT(cgs), 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; >> + } >> + >> + cgs->ready = true; >> + >> + return 0; >> +} > > Do we want to add a migration blocker here? If we keep the one that is > added when the guest transitions, we'll end up with two of them, but > that might be easier than trying to unify it. that whould be fine with me. We still need to move things around to make sure that the cpu model is already in place, though.
diff --git a/docs/confidential-guest-support.txt b/docs/confidential-guest-support.txt index f0801814ff..50b976a082 100644 --- a/docs/confidential-guest-support.txt +++ b/docs/confidential-guest-support.txt @@ -43,4 +43,7 @@ AMD Secure Encrypted Virtualization (SEV) POWER Protected Execution Facility (PEF) docs/papr-pef.txt +s390x Protected Virtualization (PV) + docs/system/s390x/protvirt.rst + Other mechanisms may be supported in future. diff --git a/docs/system/s390x/protvirt.rst b/docs/system/s390x/protvirt.rst index 712974ad87..0f481043d9 100644 --- a/docs/system/s390x/protvirt.rst +++ b/docs/system/s390x/protvirt.rst @@ -22,15 +22,22 @@ If those requirements are met, the capability `KVM_CAP_S390_PROTECTED` will indicate that KVM can support PVMs on that LPAR. -QEMU Settings -------------- +Running a Protected Virtual Machine +----------------------------------- -To indicate to the VM that it can transition into protected mode, the +To run a PVM you will need to select a CPU model which includes the `Unpack facility` (stfle bit 161 represented by the feature -`unpack`/`S390_FEAT_UNPACK`) needs to be part of the cpu model of -the VM. +`unpack`/`S390_FEAT_UNPACK`), and add these options to the command line:: + + -object s390-pv-guest,id=pv0 \ + -machine confidential-guest-support=pv0 + +Adding these options will: + +* Ensure the `unpack` facility is available +* Enable the IOMMU by default for all I/O devices +* Initialize the PV mechanism -All I/O devices need to use the IOMMU. Passthrough (vfio) devices are currently not supported. Host huge page backings are not supported. However guests can use huge diff --git a/hw/s390x/pv.c b/hw/s390x/pv.c index ab3a2482aa..319d74dfcf 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/confidential-guest-support.h" #include "hw/s390x/ipl.h" #include "hw/s390x/pv.h" @@ -111,3 +114,62 @@ 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" +OBJECT_DECLARE_SIMPLE_TYPE(S390PVGuest, S390_PV_GUEST) + +/** + * S390PVGuest: + * + * The S390PVGuest object is basically a dummy used to tell the + * confidential guest support system to use s390's PV mechanism. + * + * # $QEMU \ + * -object s390-pv-guest,id=pv0 \ + * -machine ...,confidential-guest-support=pv0 + */ +struct S390PVGuest { + ConfidentialGuestSupport parent_obj; +}; + +typedef struct S390PVGuestClass S390PVGuestClass; + +struct S390PVGuestClass { + ConfidentialGuestSupportClass parent_class; +}; + +int s390_pv_init(ConfidentialGuestSupport *cgs, Error **errp) +{ + if (!object_dynamic_cast(OBJECT(cgs), 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; + } + + cgs->ready = true; + + return 0; +} + +OBJECT_DEFINE_TYPE_WITH_INTERFACES(S390PVGuest, + s390_pv_guest, + S390_PV_GUEST, + CONFIDENTIAL_GUEST_SUPPORT, + { TYPE_USER_CREATABLE }, + { NULL }) + +static void s390_pv_guest_class_init(ObjectClass *oc, void *data) +{ +} + +static void s390_pv_guest_init(Object *obj) +{ +} + +static void s390_pv_guest_finalize(Object *obj) +{ +} diff --git a/include/hw/s390x/pv.h b/include/hw/s390x/pv.h index aee758bc2d..9bbf66f356 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(ConfidentialGuestSupport *cgs, 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..d2435664dc 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->cgs, &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 by the "confidential-guest-support" 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 confidential-guest-support 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 confidential-guest-support is set, we will either create a guest capable of entering PV mode, or fail outright. - If confidential-guest-support is not set, guests 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 confidential-guest-support=pv0 Signed-off-by: David Gibson <david@gibson.dropbear.id.au> --- docs/confidential-guest-support.txt | 3 ++ docs/system/s390x/protvirt.rst | 19 ++++++--- hw/s390x/pv.c | 62 +++++++++++++++++++++++++++++ include/hw/s390x/pv.h | 1 + target/s390x/kvm.c | 3 ++ 5 files changed, 82 insertions(+), 6 deletions(-)