The Gunners and Hammers are being linked to the Eintracht Frankfurt forward, who has 23 goals in 27 league games this season.
Many of his goals were assisted by Kostic, who is also enjoying a very good season.
Calciomercato has linked Arsenal to Silva, and Frankfurt would sell him for roughly £25 million.
"When Silva came at the beginning, it was a bit difficult because we'd never played together before and it took a while. But we soon got along well on the pitch and he understood where I was putting the balls," Kostic told the Bundesliga website.
"We often stay longer in training during the week and practise free-kicks and crosses. And that brings results.
"He reads the game very well, is always where he needs to be and, for me, the most important thing for a striker is he scores goals.
"He has been really amazing this season. Untouchable. He scores a lot for us, which is extremely important."