linux-kernel - [PATCH 5.12 011/363] kvm: Cap halt polling at kvm->max_halt_poll

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Message-Id: <20210517140302.934349093@linuxfoundation.org>
Date:   Mon, 17 May 2021 15:57:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Matlack <dmatlack@...gle.com>,
        Venkatesh Srinivas <venkateshs@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 5.12 011/363] kvm: Cap halt polling at kvm->max_halt_poll_ns

From: David Matlack <dmatlack@...gle.com>

commit 258785ef08b323bddd844b4926a32c2b2045a1b0 upstream.

When growing halt-polling, there is no check that the poll time exceeds
the per-VM limit. It's possible for vcpu->halt_poll_ns to grow past
kvm->max_halt_poll_ns and stay there until a halt which takes longer
than kvm->halt_poll_ns.

Signed-off-by: David Matlack <dmatlack@...gle.com>
Signed-off-by: Venkatesh Srinivas <venkateshs@...omium.org>
Message-Id: <20210506152442.4010298-1-venkateshs@...omium.org>
Cc: stable@...r.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 virt/kvm/kvm_main.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2758,8 +2758,8 @@ static void grow_halt_poll_ns(struct kvm
 	if (val < grow_start)
 		val = grow_start;
 
-	if (val > halt_poll_ns)
-		val = halt_poll_ns;
+	if (val > vcpu->kvm->max_halt_poll_ns)
+		val = vcpu->kvm->max_halt_poll_ns;
 
 	vcpu->halt_poll_ns = val;
 out: