linux-kernel - [PATCH 06/10] KVM: Fix hang on uniprocessor

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Message-Id: <1196594327723-git-send-email-avi@qumranet.com>
Date:	Sun,  2 Dec 2007 13:18:43 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	stable@...nel.org
Cc:	linux-kernel@...r.kernel.org, kvm-devel@...ts.sourceforge.net,
	Marko Kohtala <marko.kohtala@...il.com>,
	Avi Kivity <avi@...ranet.com>
Subject: [PATCH 06/10] KVM: Fix hang on uniprocessor

From: Marko Kohtala <marko.kohtala@...il.com>

first_cpu(cpus) returns the only CPU when NR_CPUS is 1 regardless of
the cpus mask. Therefore we avoid a kernel hang in
KVM_SET_MEMORY_REGION ioctl on uniprocessor by not entering the loop at
all.

Signed-off-by: Marko Kohtala <marko.kohtala@...il.com>
Signed-off-by: Avi Kivity <avi@...ranet.com>
---
 drivers/kvm/kvm_main.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index cd05579..b514dfb 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -273,6 +273,11 @@ void kvm_flush_remote_tlbs(struct kvm *kvm)
 			}
 	}
 
+	/* Uniprocessor kernel does not respect cpus in first_cpu. So
+	 * do not go there if we have nothing to do. */
+	if (cpus_empty(cpus))
+		return;
+
 	/*
 	 * We really want smp_call_function_mask() here.  But that's not
 	 * available, so ipi all cpus in parallel and wait for them
-- 
1.5.3

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