Spoiler: More and more countries sanction exports to Russia which creates problems for the Russian military industry complex. Russia must therefore to a higher extent than before rely on countries that is not on the Kremlin’s list of “unfriendly countries”. China is not on that list. Putin wants to replace imports from sanctioning countries by imports from China.
However, parts of the Chinese value-added shares of Russian final demand for Computers & Electronics and Machinery origin in countries that sanction Russia. Imposing secondary sanctions that prevent China from using parts and components from sanctioning countries will make it more difficult for Putin to feed his death machine.
This will not put a halt to Chinese exports to Russia. China can keep exporting products without any parts and components from sanctioning countries or produce them themselves. However, that is not easy for China in the short run. Chinese exports without parts and components from sanctioning countries appear to be less advanced and poor substitutes for the products from sanctioning countries.