[PATCH v1 1/2] KVM: arm64: Prevent 64-bit overflow when computing hyp clock rate

[Fuad Tabba]

On Thu, 8 Oct 2026 at 11:42, 'Vincent Donnefort' via kernel-team
<kernel-team at android.com> wrote:
>
> The hypervisor clock rate is delta_cycles * NSEC_PER_SEC / delta_boot.
> It is computed whenever a deviation occurs. If the delta between two
> rate updates is big enough, delta_cycles * NSEC_PER_SEC will overflow.
>
> Prevent overflow with mul_u64_u64_div_u64(). And as a bonus, simplify
> the clock estimation with mul_u64_u32_shr().
>
> Fixes: b22888917fa4 ("KVM: arm64: Sync boot clock with the nVHE/pKVM hyp")
> Cc: stable at vger.kernel.org
> Signed-off-by: Vincent Donnefort <vdonnefort at google.com>

Reviewed-by: Fuad Tabba <fuad.tabba at linux.dev>
Tested-by: Fuad Tabba <fuad.tabba at linux.dev>

Cheers,
/fuad