Re: [PATCH v7 27/36] KVM: x86: Remove pvclock_gtod_data and private timekeeping code

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] KVM references non-existent timekeeping functions and struct fields.
--

--- Patch [27]: [PATCH v7 27/36] KVM: x86: Remove pvclock_gtod_data and private timekeeping code ---
commit f5e01c2dbc04eb5669e9c80660aff5b3897195fa
Author: David Woodhouse <dwmw@amazon.co.uk>

KVM: x86: Remove pvclock_gtod_data and private timekeeping code
    
Remove the now-unused KVM-private timekeeping infrastructure:
    
 - struct pvclock_clock and struct pvclock_gtod_data
 - update_pvclock_gtod() and its seqcount-protected state copy
 - read_tsc() (KVM's private TSC reader with cycle_last clamping)
 - vgettsc() (KVM's private clocksource interpolation)
 - do_kvmclock_base(), do_monotonic(), do_realtime()

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3f660bdea8a28..26d2f24aceec5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
[ ... ]
> @@ -1455,128 +1403,6 @@ void kvm_synchronize_tsc(struct kvm_vcpu *vcpu, u64 *user_value)
>  
>  #ifdef CONFIG_X86_64
>  
> -static u64 read_tsc(void)
> -{
[ ... ]
> -static int do_realtime(struct timespec64 *ts, u64 *tsc_timestamp)
> -{
[ ... ]
> -	return mode;
> -}
> -
>  /*
>   * Calculates the kvmclock_base_ns (CLOCK_MONOTONIC_RAW + boot time) and
>   * reports the TSC value from which it do so. Returns true if host is

[Severity: Low]
Are these timekeeping functions and struct fields defined elsewhere?

With the removal of the private timekeeping code, the remaining functions
here seem to rely on undefined interfaces, which could cause a build failure.

Specifically, kvm_get_time_and_clockread() calls ktime_get_snapshot_id(),
which does not appear to be defined in the tree:

arch/x86/kvm/x86.c:kvm_get_time_and_clockread() {
    ...
    struct system_time_snapshot snap = {};

    ktime_get_snapshot_id(CLOCK_MONOTONIC_RAW, &snap);
    ...
    *kernel_ns = ktime_to_ns(ktime_mono_to_any(snap.systime, TK_OFFS_BOOT));
    ...
}

Additionally, kvm_snapshot_has_tsc() accesses several fields in
struct system_time_snapshot that are not defined, such as valid, hw_csid,
hw_cycles, and systime:

arch/x86/kvm/x86.c:kvm_snapshot_has_tsc() {
    ...
    if (!snap->valid)
        return false;

    if (snap->cs_id == CSID_X86_TSC) {
        *tsc_timestamp = snap->cycles;
        return true;
    }

    if (snap->hw_csid == CSID_X86_TSC && snap->hw_cycles) {
        *tsc_timestamp = snap->hw_cycles;
        return true;
    }
    ...
}

Could this lead to compilation errors?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260728144954.355376-1-dwmw2@infradead.org?part=27