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SubjectRe: [PATCH][next] KVM: x86: remove redundant WARN_ON check of an unsigned less than zero
On Fri, Feb 07, 2020 at 11:18:13PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.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@canonical.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);


> /* If the host uses TSC clocksource, then it is stable */
> pvclock_flags = 0;
> --
> 2.24.0
>

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