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KVM: SEV: Allow per-guest configuration of GHCB protocol version

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The GHCB protocol version may be different from one guest to the next.
Add a field to track it for each KVM instance and extend KVM_SEV_INIT2
to allow it to be configured by userspace.

Now that all SEV-ES support for GHCB protocol version 2 is in place, go
ahead and default to it when creating SEV-ES guests through the new
KVM_SEV_INIT2 interface. Keep the older KVM_SEV_ES_INIT interface
restricted to GHCB protocol version 1.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Message-ID: <20240501071048.2208265-5-michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Michael Roth 2024-05-01 02:10:48 -05:00 committed by Paolo Bonzini
parent 8d1a36e42b
commit 4af663c2f6
4 changed files with 42 additions and 6 deletions
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11
Documentation/virt/kvm/x86/amd-memory-encryption.rst
View file

@ -95,13 +95,19 @@ Returns: 0 on success, -negative on error
struct kvm_sev_init {
__u64 vmsa_features; /* initial value of features field in VMSA */
__u32 flags; /* must be 0 */
__u32 pad[9];
__u16 ghcb_version; /* maximum guest GHCB version allowed */
__u16 pad1;
__u32 pad2[8];
};
It is an error if the hypervisor does not support any of the bits that
are set in ``flags`` or ``vmsa_features``. ``vmsa_features`` must be
0 for SEV virtual machines, as they do not have a VMSA.
``ghcb_version`` must be 0 for SEV virtual machines, as they do not issue GHCB
requests. If ``ghcb_version`` is 0 for any other guest type, then the maximum
allowed guest GHCB protocol will default to version 2.
This command replaces the deprecated KVM_SEV_INIT and KVM_SEV_ES_INIT commands.
The commands did not have any parameters (the ```data``` field was unused) and
only work for the KVM_X86_DEFAULT_VM machine type (0).
@ -112,7 +118,8 @@ They behave as if:
KVM_SEV_ES_INIT
* the ``flags`` and ``vmsa_features`` fields of ``struct kvm_sev_init`` are
set to zero
set to zero, and ``ghcb_version`` is set to 0 for KVM_SEV_INIT and 1 for
KVM_SEV_ES_INIT.
If the ``KVM_X86_SEV_VMSA_FEATURES`` attribute does not exist, the hypervisor only
supports KVM_SEV_INIT and KVM_SEV_ES_INIT. In that case, note that KVM_SEV_ES_INIT

4
arch/x86/include/uapi/asm/kvm.h
View file

@ -711,7 +711,9 @@ struct kvm_sev_cmd {
struct kvm_sev_init {
__u64 vmsa_features;
__u32 flags;
__u32 pad[9];
__u16 ghcb_version;
__u16 pad1;
__u32 pad2[8];
};
struct kvm_sev_launch_start {

32
arch/x86/kvm/svm/sev.c
View file

@ -33,7 +33,8 @@
#include "cpuid.h"
#include "trace.h"
#define GHCB_VERSION_MAX 1ULL
#define GHCB_VERSION_MAX 2ULL
#define GHCB_VERSION_DEFAULT 2ULL
#define GHCB_VERSION_MIN 1ULL
#define GHCB_HV_FT_SUPPORTED GHCB_HV_FT_SNP
@ -268,12 +269,24 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp,
if (data->vmsa_features & ~valid_vmsa_features)
return -EINVAL;
if (data->ghcb_version > GHCB_VERSION_MAX || (!es_active && data->ghcb_version))
return -EINVAL;
if (unlikely(sev->active))
return -EINVAL;
sev->active = true;
sev->es_active = es_active;
sev->vmsa_features = data->vmsa_features;
sev->ghcb_version = data->ghcb_version;
/*
* Currently KVM supports the full range of mandatory features defined
* by version 2 of the GHCB protocol, so default to that for SEV-ES
* guests created via KVM_SEV_INIT2.
*/
if (sev->es_active && !sev->ghcb_version)
sev->ghcb_version = GHCB_VERSION_DEFAULT;
ret = sev_asid_new(sev);
if (ret)
@ -307,6 +320,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
{
struct kvm_sev_init data = {
.vmsa_features = 0,
.ghcb_version = 0,
};
unsigned long vm_type;
@ -314,6 +328,14 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
return -EINVAL;
vm_type = (argp->id == KVM_SEV_INIT ? KVM_X86_SEV_VM : KVM_X86_SEV_ES_VM);
/*
* KVM_SEV_ES_INIT has been deprecated by KVM_SEV_INIT2, so it will
* continue to only ever support the minimal GHCB protocol version.
*/
if (vm_type == KVM_X86_SEV_ES_VM)
data.ghcb_version = GHCB_VERSION_MIN;
return __sev_guest_init(kvm, argp, &data, vm_type);
}
@ -2897,6 +2919,7 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
{
struct vmcb_control_area *control = &svm->vmcb->control;
struct kvm_vcpu *vcpu = &svm->vcpu;
struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info;
u64 ghcb_info;
int ret = 1;
@ -2907,7 +2930,7 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
switch (ghcb_info) {
case GHCB_MSR_SEV_INFO_REQ:
set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
set_ghcb_msr(svm, GHCB_MSR_SEV_INFO((__u64)sev->ghcb_version,
GHCB_VERSION_MIN,
sev_enc_bit));
break;
@ -3268,11 +3291,14 @@ void sev_init_vmcb(struct vcpu_svm *svm)
void sev_es_vcpu_reset(struct vcpu_svm *svm)
{
struct kvm_vcpu *vcpu = &svm->vcpu;
struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info;
/*
* Set the GHCB MSR value as per the GHCB specification when emulating
* vCPU RESET for an SEV-ES guest.
*/
set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
set_ghcb_msr(svm, GHCB_MSR_SEV_INFO((__u64)sev->ghcb_version,
GHCB_VERSION_MIN,
sev_enc_bit));
}

1
arch/x86/kvm/svm/svm.h
View file

@ -87,6 +87,7 @@ struct kvm_sev_info {
struct list_head regions_list; /* List of registered regions */
u64 ap_jump_table; /* SEV-ES AP Jump Table address */
u64 vmsa_features;
u16 ghcb_version; /* Highest guest GHCB protocol version allowed */
struct kvm *enc_context_owner; /* Owner of copied encryption context */
struct list_head mirror_vms; /* List of VMs mirroring */
struct list_head mirror_entry; /* Use as a list entry of mirrors */