path: root/virt
diff options
authorNathan Tempelman <>2021-04-08 22:32:14 +0000
committerPaolo Bonzini <>2021-04-21 12:20:02 -0400
commit54526d1fd59338fd6a381dbd806b7ccbae3aa4aa (patch)
tree658e7a672bba151def521aafa5433c5cd04bed1b /virt
parentee695f22b54a4b79753fdaa78cbbff1064050d13 (diff)
KVM: x86: Support KVM VMs sharing SEV context
Add a capability for userspace to mirror SEV encryption context from one vm to another. On our side, this is intended to support a Migration Helper vCPU, but it can also be used generically to support other in-guest workloads scheduled by the host. The intention is for the primary guest and the mirror to have nearly identical memslots. The primary benefits of this are that: 1) The VMs do not share KVM contexts (think APIC/MSRs/etc), so they can't accidentally clobber each other. 2) The VMs can have different memory-views, which is necessary for post-copy migration (the migration vCPUs on the target need to read and write to pages, when the primary guest would VMEXIT). This does not change the threat model for AMD SEV. Any memory involved is still owned by the primary guest and its initial state is still attested to through the normal SEV_LAUNCH_* flows. If userspace wanted to circumvent SEV, they could achieve the same effect by simply attaching a vCPU to the primary VM. This patch deliberately leaves userspace in charge of the memslots for the mirror, as it already has the power to mess with them in the primary guest. This patch does not support SEV-ES (much less SNP), as it does not handle handing off attested VMSAs to the mirror. For additional context, we need a Migration Helper because SEV PSP migration is far too slow for our live migration on its own. Using an in-guest migrator lets us speed this up significantly. Signed-off-by: Nathan Tempelman <> Message-Id: <> Signed-off-by: Paolo Bonzini <>
Diffstat (limited to 'virt')
1 files changed, 6 insertions, 0 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 545a28387c33..48c1e4842908 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4197,6 +4197,12 @@ static struct file_operations kvm_vm_fops = {
+bool file_is_kvm(struct file *file)
+ return file && file->f_op == &kvm_vm_fops;
static int kvm_dev_ioctl_create_vm(unsigned long type)
int r;