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| author | Paolo Bonzini <pbonzini@redhat.com> | 2016-06-27 15:08:01 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-07-01 11:03:39 +0200 |
| commit | 9175d2e97b08e86293e68246020a5c29f88aa674 (patch) | |
| tree | cb8268447f8a95149214b807c987d7d84f0dc098 | |
| parent | f2485b3e0c6c0aa3a9546babc2fad3739e964ebb (diff) | |
| download | op-kernel-dev-9175d2e97b08e86293e68246020a5c29f88aa674.zip op-kernel-dev-9175d2e97b08e86293e68246020a5c29f88aa674.tar.gz | |
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>
| -rw-r--r-- | arch/x86/kvm/vmx.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index c1d655c..85e2f0a 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -10829,9 +10829,9 @@ 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 && |
