KVM: arm64: Prevent 64-bit overflow when computing hyp clock rate

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@vger.kernel.org
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20261008104212.3134550-2-vdonnefort@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

0 files changed, 0 insertions, 0 deletions