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authorPaolo Bonzini <pbonzini@redhat.com>2016-06-27 15:08:01 +0200
committerYunhong Jiang <yunhong.jiang@linux.intel.com>2016-07-18 08:07:47 -0700
commit6443c73ab06239ab4b1bc0511d9b78f7122f477d (patch)
treec65a21f9088c9807a55e6aa42fb87c4a34f9ed2d /kernel/arch/x86/kvm/vmx.c
parent09c7dd2e0b05c5bc2def37e525a98e6b344d56f5 (diff)
KVM: vmx: fix underflow in TSC deadline calculation
If the TSC deadline timer is programmed really close to the deadline or even in the past, the computation in vmx_set_hv_timer can underflow and cause delta_tsc to be set to a huge value. This generally results in vmx_set_hv_timer returning -ERANGE, but we can fix it by limiting delta_tsc to be positive or zero. Reported-by: Wanpeng Li <wanpeng.li@hotmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Change-Id: I12eea18c3ec648dbf782d7754b7b574d7d6aa92c upstream-status: backport Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Diffstat (limited to 'kernel/arch/x86/kvm/vmx.c')
-rw-r--r--kernel/arch/x86/kvm/vmx.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/arch/x86/kvm/vmx.c b/kernel/arch/x86/kvm/vmx.c
index e378975f5..5da019be6 100644
--- a/kernel/arch/x86/kvm/vmx.c
+++ b/kernel/arch/x86/kvm/vmx.c
@@ -10663,9 +10663,9 @@ static inline int u64_shl_div_u64(u64 a, unsigned int shift,
static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- u64 tscl = rdtsc(), delta_tsc;
-
- delta_tsc = guest_deadline_tsc - kvm_read_l1_tsc(vcpu, tscl);
+ u64 tscl = rdtsc();
+ u64 guest_tscl = kvm_read_l1_tsc(vcpu, tscl);
+ u64 delta_tsc = max(guest_deadline_tsc, guest_tscl) - guest_tscl;
/* Convert to host delta tsc if tsc scaling is enabled */
if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio &&