On Tue, 2 Feb 2021 15:13:12 +1100
David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote:
> Some upcoming POWER machines have a system called PEF (Protected
> Execution Facility) which uses a small ultravisor to allow guests to
> run in a way that they can't be eavesdropped by the hypervisor. The
> effect is roughly similar to AMD SEV, although the mechanisms are
> quite different.
>
> Most of the work of this is done between the guest, KVM and the
> ultravisor, with little need for involvement by qemu. However qemu
> does need to tell KVM to allow secure VMs.
>
> Because the availability of secure mode is a guest visible difference
> which depends on having the right hardware and firmware, we don't
> enable this by default. In order to run a secure guest you need to
> create a "pef-guest" object and set the confidential-guest-support
> property to point to it.
>
> Note that this just *allows* secure guests, the architecture of PEF is
> such that the guest still needs to talk to the ultravisor to enter
> secure mode. Qemu has no direct way of knowing if the guest is in
> secure mode, and certainly can't know until well after machine
> creation time.
>
> To start a PEF-capable guest, use the command line options:
> -object pef-guest,id=pef0 -machine confidential-guest-support=pef0
>
> Signed-off-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
Reviewed-by: Greg Kurz <groug@xxxxxxxx>
Just some cosmetic comments in case you need to respin. See below.
> docs/confidential-guest-support.txt | 3 +
> docs/papr-pef.txt | 30 +++++++
> hw/ppc/meson.build | 1 +
> hw/ppc/pef.c | 133 ++++++++++++++++++++++++++++
> hw/ppc/spapr.c | 8 +-
> include/hw/ppc/pef.h | 17 ++++
> target/ppc/kvm.c | 18 ----
> target/ppc/kvm_ppc.h | 6 --
> 8 files changed, 191 insertions(+), 25 deletions(-)
> create mode 100644 docs/papr-pef.txt
> create mode 100644 hw/ppc/pef.c
> create mode 100644 include/hw/ppc/pef.h
>
> diff --git a/docs/confidential-guest-support.txt b/docs/confidential-guest-support.txt
> index bd439ac800..4da4c91bd3 100644
> --- a/docs/confidential-guest-support.txt
> +++ b/docs/confidential-guest-support.txt
> @@ -40,4 +40,7 @@ Currently supported confidential guest mechanisms are:
> AMD Secure Encrypted Virtualization (SEV)
> docs/amd-memory-encryption.txt
>
> +POWER Protected Execution Facility (PEF)
> + docs/papr-pef.txt
> +
> Other mechanisms may be supported in future.
> diff --git a/docs/papr-pef.txt b/docs/papr-pef.txt
> new file mode 100644
> index 0000000000..72550e9bf8
> --- /dev/null
> +++ b/docs/papr-pef.txt
> @@ -0,0 +1,30 @@
> +POWER (PAPR) Protected Execution Facility (PEF)
> +===============================================
> +
> +Protected Execution Facility (PEF), also known as Secure Guest support
> +is a feature found on IBM POWER9 and POWER10 processors.
> +
> +If a suitable firmware including an Ultravisor is installed, it adds
> +an extra memory protection mode to the CPU. The ultravisor manages a
> +pool of secure memory which cannot be accessed by the hypervisor.
> +
> +When this feature is enabled in QEMU, a guest can use ultracalls to
> +enter "secure mode". This transfers most of its memory to secure
> +memory, where it cannot be eavesdropped by a compromised hypervisor.
> +
> +Launching
> +---------
> +
> +To launch a guest which will be permitted to enter PEF secure mode:
> +
> +# ${QEMU} \
> + -object pef-guest,id=pef0 \
> + -machine confidential-guest-support=pef0 \
> + ...
> +
> +Live Migration
> +----------------
> +
> +Live migration is not yet implemented for PEF guests. For
> +consistency, we currently prevent migration if the PEF feature is
> +enabled, whether or not the guest has actually entered secure mode.
> diff --git a/hw/ppc/meson.build b/hw/ppc/meson.build
> index ffa2ec37fa..218631c883 100644
> --- a/hw/ppc/meson.build
> +++ b/hw/ppc/meson.build
> @@ -27,6 +27,7 @@ ppc_ss.add(when: 'CONFIG_PSERIES', if_true: files(
> 'spapr_nvdimm.c',
> 'spapr_rtas_ddw.c',
> 'spapr_numa.c',
> + 'pef.c',
> ))
> ppc_ss.add(when: 'CONFIG_SPAPR_RNG', if_true: files('spapr_rng.c'))
> ppc_ss.add(when: ['CONFIG_PSERIES', 'CONFIG_LINUX'], if_true: files(
> diff --git a/hw/ppc/pef.c b/hw/ppc/pef.c
> new file mode 100644
> index 0000000000..f9fd1f2a71
> --- /dev/null
> +++ b/hw/ppc/pef.c
> @@ -0,0 +1,133 @@
> +/*
> + * PEF (Protected Execution Facility) for POWER support
> + *
> + * Copyright Red Hat.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "qemu/osdep.h"
> +
> +#include "qapi/error.h"
> +#include "qom/object_interfaces.h"
> +#include "sysemu/kvm.h"
> +#include "migration/blocker.h"
> +#include "exec/confidential-guest-support.h"
> +#include "hw/ppc/pef.h"
> +
> +#define TYPE_PEF_GUEST "pef-guest"
> +OBJECT_DECLARE_SIMPLE_TYPE(PefGuest, PEF_GUEST)
> +
> +typedef struct PefGuest PefGuest;
> +typedef struct PefGuestClass PefGuestClass;
> +
> +struct PefGuestClass {
> + ConfidentialGuestSupportClass parent_class;
> +};
> +
> +/**
> + * PefGuest:
> + *
> + * The PefGuest object is used for creating and managing a PEF
> + * guest.
> + *
> + * # $QEMU \
> + * -object pef-guest,id=pef0 \
> + * -machine ...,confidential-guest-support=pef0
> + */
> +struct PefGuest {
> + ConfidentialGuestSupport parent_obj;
> +};
> +
> +static int kvmppc_svm_init(Error **errp)
FWIW, this function could return bool.
> +{
> +#ifdef CONFIG_KVM
> + if (!kvm_check_extension(kvm_state, KVM_CAP_PPC_SECURE_GUEST)) {
> + error_setg(errp,
> + "KVM implementation does not support Secure VMs (is an ultravisor running?)");
> + return -1;
> + } else {
> + int ret = kvm_vm_enable_cap(kvm_state, KVM_CAP_PPC_SECURE_GUEST, 0, 1);
> +
> + if (ret < 0) {
> + error_setg(errp,
> + "Error enabling PEF with KVM");
> + return -1;
> + }
> + }
> +
> + return 0;
> +#else
> + g_assert_not_reached();
> +#endif
> +}
> +
> +/*
> + * Don't set error if KVM_PPC_SVM_OFF ioctl is invoked on kernels
> + * that don't support this ioctl.
> + */
> +static int kvmppc_svm_off(Error **errp)
> +{
> +#ifdef CONFIG_KVM
> + int rc;
> +
> + rc = kvm_vm_ioctl(KVM_STATE(current_accel()), KVM_PPC_SVM_OFF);
> + if (rc && rc != -ENOTTY) {
> + error_setg_errno(errp, -rc, "KVM_PPC_SVM_OFF ioctl failed");
> + return rc;
The ultimate caller for this is spapr_machine_reset() which doesn't
care for a return value since it passes &error_fatal. Is there any
chance that callers ever need to know about the errno value actually ?
If not, it looks like this could return bool all the same.
> + }
> + return 0;
> +#else
> + g_assert_not_reached();
> +#endif
> +}
> +
> +int pef_kvm_init(ConfidentialGuestSupport *cgs, Error **errp)
Ditto.
> +{
> + if (!object_dynamic_cast(OBJECT(cgs), TYPE_PEF_GUEST)) {
> + return 0;
> + }
> +
> + if (!kvm_enabled()) {
> + error_setg(errp, "PEF requires KVM");
> + return -1;
> + }
> +
> + return kvmppc_svm_init(errp);
> +}
> +
> +int pef_kvm_reset(ConfidentialGuestSupport *cgs, Error **errp)
Ditto.
> +{
> + if (!object_dynamic_cast(OBJECT(cgs), TYPE_PEF_GUEST)) {
> + return 0;
> + }
> +
> + /*
> + * If we don't have KVM we should never have been able to
> + * initialize PEF, so we should never get this far
> + */
> + assert(kvm_enabled());
> +
> + return kvmppc_svm_off(errp);
> +}
> +
> +OBJECT_DEFINE_TYPE_WITH_INTERFACES(PefGuest,
> + pef_guest,
> + PEF_GUEST,
> + CONFIDENTIAL_GUEST_SUPPORT,
> + { TYPE_USER_CREATABLE },
> + { NULL })
> +
> +static void pef_guest_class_init(ObjectClass *oc, void *data)
> +{
> +}
> +
> +static void pef_guest_init(Object *obj)
> +{
> +}
> +
> +static void pef_guest_finalize(Object *obj)
> +{
> +}
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6c47466fc2..612356e9ec 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -83,6 +83,7 @@
> #include "hw/ppc/spapr_tpm_proxy.h"
> #include "hw/ppc/spapr_nvdimm.h"
> #include "hw/ppc/spapr_numa.h"
> +#include "hw/ppc/pef.h"
>
> #include "monitor/monitor.h"
>
> @@ -1574,7 +1575,7 @@ static void spapr_machine_reset(MachineState *machine)
> void *fdt;
> int rc;
>
> - kvmppc_svm_off(&error_fatal);
> + pef_kvm_reset(machine->cgs, &error_fatal);
> spapr_caps_apply(spapr);
>
> first_ppc_cpu = POWERPC_CPU(first_cpu);
> @@ -2658,6 +2659,11 @@ static void spapr_machine_init(MachineState *machine)
> char *filename;
> Error *resize_hpt_err = NULL;
>
> + /*
> + * if Secure VM (PEF) support is configured, then initialize it
> + */
> + pef_kvm_init(machine->cgs, &error_fatal);
> +
> msi_nonbroken = true;
>
> QLIST_INIT(&spapr->phbs);
> diff --git a/include/hw/ppc/pef.h b/include/hw/ppc/pef.h
> new file mode 100644
> index 0000000000..707dbe524c
> --- /dev/null
> +++ b/include/hw/ppc/pef.h
> @@ -0,0 +1,17 @@
> +/*
> + * PEF (Protected Execution Facility) for POWER support
> + *
> + * Copyright Red Hat.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef HW_PPC_PEF_H
> +#define HW_PPC_PEF_H
> +
> +int pef_kvm_init(ConfidentialGuestSupport *cgs, Error **errp);
> +int pef_kvm_reset(ConfidentialGuestSupport *cgs, Error **errp);
> +
> +#endif /* HW_PPC_PEF_H */
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index daf690a678..0c5056dd5b 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -2929,21 +2929,3 @@ void kvmppc_set_reg_tb_offset(PowerPCCPU *cpu, int64_t tb_offset)
> kvm_set_one_reg(cs, KVM_REG_PPC_TB_OFFSET, &tb_offset);
> }
> }
> -
> -/*
> - * Don't set error if KVM_PPC_SVM_OFF ioctl is invoked on kernels
> - * that don't support this ioctl.
> - */
> -void kvmppc_svm_off(Error **errp)
> -{
> - int rc;
> -
> - if (!kvm_enabled()) {
> - return;
> - }
> -
> - rc = kvm_vm_ioctl(KVM_STATE(current_accel()), KVM_PPC_SVM_OFF);
> - if (rc && rc != -ENOTTY) {
> - error_setg_errno(errp, -rc, "KVM_PPC_SVM_OFF ioctl failed");
> - }
> -}
> diff --git a/target/ppc/kvm_ppc.h b/target/ppc/kvm_ppc.h
> index 73ce2bc951..989f61ace0 100644
> --- a/target/ppc/kvm_ppc.h
> +++ b/target/ppc/kvm_ppc.h
> @@ -39,7 +39,6 @@ int kvmppc_booke_watchdog_enable(PowerPCCPU *cpu);
> target_ulong kvmppc_configure_v3_mmu(PowerPCCPU *cpu,
> bool radix, bool gtse,
> uint64_t proc_tbl);
> -void kvmppc_svm_off(Error **errp);
> #ifndef CONFIG_USER_ONLY
> bool kvmppc_spapr_use_multitce(void);
> int kvmppc_spapr_enable_inkernel_multitce(void);
> @@ -216,11 +215,6 @@ static inline target_ulong kvmppc_configure_v3_mmu(PowerPCCPU *cpu,
> return 0;
> }
>
> -static inline void kvmppc_svm_off(Error **errp)
> -{
> - return;
> -}
> -
> static inline void kvmppc_set_reg_ppc_online(PowerPCCPU *cpu,
> unsigned int online)
> {
