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KVM: SEV: cleanup locking for KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM

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Encapsulate the handling of the migration_in_progress flag for both VMs in
two functions sev_lock_two_vms and sev_unlock_two_vms.  It does not matter
if KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM locks the destination struct kvm a bit
later, and this change 1) keeps the cleanup chain of labels smaller 2)
makes it possible for KVM_CAP_VM_COPY_ENC_CONTEXT_FROM to reuse the logic.

Cc: Peter Gonda <pgonda@google.com>
Cc: Sean Christopherson <seanjc@google.com>
Message-Id: <20211123005036.2954379-6-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2021-11-22 19:50:29 -05:00
parent 4674164f0a
commit 501b580c02
1 changed files with 27 additions and 26 deletions
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53
arch/x86/kvm/svm/sev.c
View File

@ -1543,28 +1543,40 @@ static bool is_cmd_allowed_from_mirror(u32 cmd_id)
return false;
}
static int sev_lock_for_migration(struct kvm *kvm)
static int sev_lock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
struct kvm_sev_info *dst_sev = &to_kvm_svm(dst_kvm)->sev_info;
struct kvm_sev_info *src_sev = &to_kvm_svm(src_kvm)->sev_info;
if (dst_kvm == src_kvm)
return -EINVAL;
/*
* Bail if this VM is already involved in a migration to avoid deadlock
* between two VMs trying to migrate to/from each other.
* Bail if these VMs are already involved in a migration to avoid
* deadlock between two VMs trying to migrate to/from each other.
*/
if (atomic_cmpxchg_acquire(&sev->migration_in_progress, 0, 1))
if (atomic_cmpxchg_acquire(&dst_sev->migration_in_progress, 0, 1))
return -EBUSY;
mutex_lock(&kvm->lock);
if (atomic_cmpxchg_acquire(&src_sev->migration_in_progress, 0, 1)) {
atomic_set_release(&dst_sev->migration_in_progress, 0);
return -EBUSY;
}
mutex_lock(&dst_kvm->lock);
mutex_lock(&src_kvm->lock);
return 0;
}
static void sev_unlock_after_migration(struct kvm *kvm)
static void sev_unlock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
{
struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
struct kvm_sev_info *dst_sev = &to_kvm_svm(dst_kvm)->sev_info;
struct kvm_sev_info *src_sev = &to_kvm_svm(src_kvm)->sev_info;
mutex_unlock(&kvm->lock);
atomic_set_release(&sev->migration_in_progress, 0);
mutex_unlock(&dst_kvm->lock);
mutex_unlock(&src_kvm->lock);
atomic_set_release(&dst_sev->migration_in_progress, 0);
atomic_set_release(&src_sev->migration_in_progress, 0);
}
@ -1665,15 +1677,6 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
bool charged = false;
int ret;
ret = sev_lock_for_migration(kvm);
if (ret)
return ret;
if (sev_guest(kvm)) {
ret = -EINVAL;
goto out_unlock;
}
source_kvm_file = fget(source_fd);
if (!file_is_kvm(source_kvm_file)) {
ret = -EBADF;
@ -1681,13 +1684,13 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
}
source_kvm = source_kvm_file->private_data;
ret = sev_lock_for_migration(source_kvm);
ret = sev_lock_two_vms(kvm, source_kvm);
if (ret)
goto out_fput;
if (!sev_guest(source_kvm)) {
if (sev_guest(kvm) || !sev_guest(source_kvm)) {
ret = -EINVAL;
goto out_source;
goto out_unlock;
}
src_sev = &to_kvm_svm(source_kvm)->sev_info;
@ -1727,13 +1730,11 @@ out_dst_cgroup:
sev_misc_cg_uncharge(cg_cleanup_sev);
put_misc_cg(cg_cleanup_sev->misc_cg);
cg_cleanup_sev->misc_cg = NULL;
out_source:
sev_unlock_after_migration(source_kvm);
out_unlock:
sev_unlock_two_vms(kvm, source_kvm);
out_fput:
if (source_kvm_file)
fput(source_kvm_file);
out_unlock:
sev_unlock_after_migration(kvm);
return ret;
}