From 8422109c3b8f62e0645fdcc3bb550f7550a502a0 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 22 Nov 2021 19:50:36 -0500
Subject: [PATCH 2/6] KVM: SEV: accept signals in sev_lock_two_vms
Git-commit: c9d61dcb0bc26a761dc84a87bd8a0d3b3c432f10
Patch-mainline: v5.16-rc4
References: bsc#1194526

Generally, kvm->lock is not taken for a long time, but
sev_lock_two_vms is different: it takes vCPU locks
inside, so userspace can hold it back just by calling
a vCPU ioctl.  Play it safe and use mutex_lock_killable.

Message-Id: <20211123005036.2954379-13-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 | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 4c2b475473e0..cec32c4548f0 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1548,6 +1548,7 @@ static int sev_lock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
 {
 	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;
+	int r = -EBUSY;
 
 	if (dst_kvm == src_kvm)
 		return -EINVAL;
@@ -1559,14 +1560,23 @@ static int sev_lock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
 	if (atomic_cmpxchg_acquire(&dst_sev->migration_in_progress, 0, 1))
 		return -EBUSY;
 
-	if (atomic_cmpxchg_acquire(&src_sev->migration_in_progress, 0, 1)) {
-		atomic_set_release(&dst_sev->migration_in_progress, 0);
-		return -EBUSY;
-	}
+	if (atomic_cmpxchg_acquire(&src_sev->migration_in_progress, 0, 1))
+		goto release_dst;
 
-	mutex_lock(&dst_kvm->lock);
-	mutex_lock(&src_kvm->lock);
+	r = -EINTR;
+	if (mutex_lock_killable(&dst_kvm->lock))
+		goto release_src;
+	if (mutex_lock_killable(&src_kvm->lock))
+		goto unlock_dst;
 	return 0;
+
+unlock_dst:
+	mutex_unlock(&dst_kvm->lock);
+release_src:
+	atomic_set_release(&src_sev->migration_in_progress, 0);
+release_dst:
+	atomic_set_release(&dst_sev->migration_in_progress, 0);
+	return r;
 }
 
 static void sev_unlock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
-- 
2.31.1