diff options
| author |   Paolo Bonzini <pbonzini@redhat.com> | 2016-06-27 15:08:01 +0200 |
|---|---|---|
| committer |   Yunhong Jiang <yunhong.jiang@linux.intel.com> | 2016-07-18 08:07:47 -0700 |
| commit | 6443c73ab06239ab4b1bc0511d9b78f7122f477d (patch) | |
| tree | c65a21f9088c9807a55e6aa42fb87c4a34f9ed2d | |
| parent | 09c7dd2e0b05c5bc2def37e525a98e6b344d56f5 (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>
| -rw-r--r-- | kernel/arch/x86/kvm/vmx.c | 6 |
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 && |