This is a very good question. There are multiple key factors that influence China's actions in Eastern Europe in general but due to the narrow scope of this question let's focus on solely China's position in Ukraine-Russia talks.
China has a major interest in conducting business in Ukraine as indicated by China being the largest import trade partner, with 2021 setting a new record of $15,76 billion and Ukraine being the largest sunflower oil and corn seller to China. Not only that, but China is encouraging the adoption of the infamous "One Belt One Road" initiative as indicated by China-Ukraine infrastructure partnership. (Source: an interview with the Chinese ambassador in Ukraine).
Politics wise, the current Ukrainian government as well as some of Ukraine's political elites seem to be favourable towards China, as indicated by the presence of high-ranking officials on China-related official events, Ukraine withdrawing their support of Canada's UN Human Rights statement regarding the treatment of Uyghurs in China and many other political "favours" done by both sides. This, topped with a borderline insane statement of David Arakhamiya (who is the leader of current largest political party in Ukraine "Sluga Narodu" which hold the majority in Ukraine's Parliament and is also the party of Ukraine's current President Volodymyr Zelensky) that the CCP and "Sluga Narodu" principles align (despite "Sluga Narodu" previously claiming to be libertarian Source) presents a clear pattern of being quite warm towards China (More elaborate recount of current Ukrainian governments China favoritism).
This behaviour is very odd and raises a lot of eyebrows, considering that China has a history of voting against Ukraine on matters that are important to Ukraine.
The image above indicates Chinas UN voting pattern regarding Crimea, which is another issue that involves both Ukraine and Russia. (China is under the number 78 on that list).
Now let's take a look at China-Russia relationships. The trade turnover between both countries in 2021 was $146.88 bln. Just like current Ukrainian government, politics wise, Russia seems to be favorable towards China, so much that they "leased" some parts of Russia to the Chinese (Source). Not only that, but China seems to be interested in having Russia as a gas supplier via the "Sila Sibiri" gas line (Source).
So where does this bring us? China has economical interests in both countries, which is clearly illustrated by the everincreasing trade volume. China also has political interests in both countries so what China does in this situation is attempting to stay "neutral": not breaking their relationship with Russia but also ensuring that their political and economical developments in Ukraine remain.
As if to whether they are siding with anyone...well, it's no secret that China is the largest trading partner for the U.S. so make of that what you will. Rhetorics and claims wise on this issue, China is most likely going won't change the hostile stance towards the US that they have developed over the years (among with the constantly rising trade turnover with the US...), but will mostly likely try to find a middleground between Ukraine and Russia (their relatively new economical/political development and the existing one).