FAILED: patch "[PATCH] KVM: X86: Do not yield to self" failed to apply to 5.4-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a1fa4cbd53d9bc7bb0eaa7bcf7c8a5904372a4ec Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpengli@tencent.com>
Date: Fri, 9 Apr 2021 12:18:31 +0800
Subject: [PATCH] KVM: X86: Do not yield to self

If the target is self we do not need to yield, we can avoid malicious
guest to play this.

Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Message-Id: <1617941911-5338-3-git-send-email-wanpengli@tencent.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 05a4bce181d7..66d2ab074a5f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8228,6 +8228,10 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id)
 	if (!target || !READ_ONCE(target->ready))
 		goto no_yield;
 
+	/* Ignore requests to yield to self */
+	if (vcpu == target)
+		goto no_yield;
+
 	if (kvm_vcpu_yield_to(target) <= 0)
 		goto no_yield;