[PATCH 5.14 058/172] KVM: SEV: Allow some commands for mirror VM

Greg Kroah-Hartman
2021-10-04T13:35:45Z

From: Peter Gonda <pgonda@google.com>

commit 5b92b6ca92b65bef811048c481e4446f4828500a upstream.

A mirrored SEV-ES VM will need to call KVM_SEV_LAUNCH_UPDATE_VMSA to
setup its vCPUs and have them measured, and their VMSAs encrypted. Without
this change, it is impossible to have mirror VMs as part of SEV-ES VMs.

Also allow the guest status check and debugging commands since they do
not change any guest state.

Signed-off-by: Peter Gonda <pgonda@google.com>
Cc: Marc Orr <marcorr@google.com>
Cc: Nathan Tempelman <natet@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Steve Rutherford <srutherford@google.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: 54526d1fd593 ("KVM: x86: Support KVM VMs sharing SEV context", 2021-04-21)
Message-Id: <20210921150345.2221634-3-pgonda@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/svm/sev.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1509,6 +1509,20 @@ static int sev_receive_finish(struct kvm
return sev_issue_cmd(kvm, SEV_CMD_RECEIVE_FINISH, &data, &argp->error);
}

+static bool cmd_allowed_from_miror(u32 cmd_id)
+{
+ /*
+ * Allow mirrors VM to call KVM_SEV_LAUNCH_UPDATE_VMSA to enable SEV-ES
+ * active mirror VMs. Also allow the debugging and status commands.
+ */
+ if (cmd_id == KVM_SEV_LAUNCH_UPDATE_VMSA ||
+ cmd_id == KVM_SEV_GUEST_STATUS || cmd_id == KVM_SEV_DBG_DECRYPT ||
+ cmd_id == KVM_SEV_DBG_ENCRYPT)
+ return true;
+
+ return false;
+}
+
int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
{
struct kvm_sev_cmd sev_cmd;
@@ -1525,8 +1539,9 @@ int svm_mem_enc_op(struct kvm *kvm, void

mutex_lock(&kvm->lock);

- /* enc_context_owner handles all memory enc operations */
- if (is_mirroring_enc_context(kvm)) {
+ /* Only the enc_context_owner handles some memory enc operations. */
+ if (is_mirroring_enc_context(kvm) &&
+ !cmd_allowed_from_miror(sev_cmd.id)) {
r = -EINVAL;
goto out;
}