Messages in this thread | | | Subject | Re: [PATCH 2/2] KVM: x86: use raw clock values consistently | From | Paolo Bonzini <> | Date | Thu, 23 Jan 2020 14:54:47 +0100 |
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On 23/01/20 14:43, Vitaly Kuznetsov wrote: >> + >> +static s64 get_kvmclock_base_ns(void) >> +{ >> + /* Count up from boot time, but with the frequency of the raw clock. */ >> + return ktime_to_ns(ktime_add(ktime_get_raw(), pvclock_gtod_data.offs_boot)); >> +} >> +#else >> +static s64 get_kvmclock_base_ns(void) >> +{ >> + /* Master clock not used, so we can just use CLOCK_BOOTTIME. */ >> + return ktime_get_boottime_ns(); >> +} >> #endif > But we could've still used the RAW+offs_boot version, right? And this is > just to basically preserve the existing behavior on !x86.
Yes, there's no reason to restrict the pvclock_gtod notifier to x86_64. But this is stable material so I kept it easy.
>> >> - getboottime64(&boot); >> + wall_nsec = ktime_get_real_ns() - get_kvmclock_ns(kvm); > > There are not that many hosts with more than 50 years uptime and likely > none running Linux with live kernel patching support so I bet noone will > ever see this overflowing, however, as wall_nsec is u64 and we're > dealing with kvmclock here I'd suggest to add a WARN_ON().
You're off by a factor of 10, 2^64 nanoseconds are about 584 years (584*365*10^9*86400). :)
Paolo
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