From 54acdf8950bbab8afc25537f37080cc1d37ac386 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 22 Nov 2021 19:50:29 -0500
Subject: [PATCH 4/6] KVM: SEV: cleanup locking for
KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM
Git-commit: 501b580c02339a83917cf3b44c445f2419b15dcb
Patch-mainline: 5.16-rc4
References: bsc#1194526
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>
Signed-off-by: Li Zhang <lizhang@suse.de>
---
arch/x86/kvm/svm/sev.c | 53 +++++++++++++++++++++---------------------
1 file changed, 27 insertions(+), 26 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index d43242ba46c2..f4c01d24dd96 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1545,28 +1545,40 @@ static bool cmd_allowed_from_miror(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);
}
@@ -1667,15 +1679,6 @@ 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;
@@ -1683,13 +1686,13 @@ 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;
@@ -1729,13 +1732,11 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
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;
}
--
2.31.1