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authorDavid Matlack <dmatlack@google.com>2016-03-08 16:19:44 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-03-16 08:42:58 -0700
commitc9e1bbef7e774dd315fb7f2e239c39cd2bb9674b (patch)
treec0ca615c6e371764bfd367783667c6eab87b34fc /virt
parent431c9f011595ab1dc5ccac2d7d094b5a6bd519a4 (diff)
downloadlinux-linaro-stable-c9e1bbef7e774dd315fb7f2e239c39cd2bb9674b.tar.gz
kvm: cap halt polling at exactly halt_poll_ns
commit 313f636d5c490c9741d3f750dc8da33029edbc6b upstream. When growing halt-polling, there is no check that the poll time exceeds the limit. It's possible for vcpu->halt_poll_ns grow once past halt_poll_ns, and stay there until a halt which takes longer than vcpu->halt_poll_ns. For example, booting a Linux guest with halt_poll_ns=11000: ... kvm:kvm_halt_poll_ns: vcpu 0: halt_poll_ns 0 (shrink 10000) ... kvm:kvm_halt_poll_ns: vcpu 0: halt_poll_ns 10000 (grow 0) ... kvm:kvm_halt_poll_ns: vcpu 0: halt_poll_ns 20000 (grow 10000) Signed-off-by: David Matlack <dmatlack@google.com> Fixes: aca6ff29c4063a8d467cdee241e6b3bf7dc4a171 Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/kvm_main.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 484079efea5b..7338e30421d8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1961,6 +1961,9 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
else
val *= halt_poll_ns_grow;
+ if (val > halt_poll_ns)
+ val = halt_poll_ns;
+
vcpu->halt_poll_ns = val;
trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
}