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Date: Wed, 12 Feb 2020 13:32:06 +0100 From: Paolo Bonzini <pbonzini@...hat.com> To: Sean Christopherson <sean.j.christopherson@...el.com>, Colin King <colin.king@...onical.com> Cc: Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org, kvm@...r.kernel.org, kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH][next] KVM: x86: remove redundant WARN_ON check of an unsigned less than zero On 08/02/20 01:47, Sean Christopherson wrote: > On Fri, Feb 07, 2020 at 11:18:13PM +0000, Colin King wrote: >> From: Colin Ian King <colin.king@...onical.com> >> >> The check cpu->hv_clock.system_time < 0 is redundant since system_time >> is a u64 and hence can never be less than zero. Remove it. >> >> Addresses-Coverity: ("Macro compares unsigned to 0") >> Signed-off-by: Colin Ian King <colin.king@...onical.com> >> --- >> arch/x86/kvm/x86.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index fbabb2f06273..d4967ac47e68 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -2448,7 +2448,6 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) >> vcpu->hv_clock.tsc_timestamp = tsc_timestamp; >> vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset; >> vcpu->last_guest_tsc = tsc_timestamp; >> - WARN_ON(vcpu->hv_clock.system_time < 0); > > Don't know this code well, but @kernel_ns and @v->kvm->arch.kvmclock_offset > are both s64, so maybe this was intended and/or desirable? > > WARN_ON((s64)vcpu->hv_clock.system_time < 0); Yes, that's related to the bugfix where kvmclock would get negative. I queued the patch with the (s64) cast added. Thanks to both of you! Paolo
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