Higher performance hardware such as graphics cards use DMA to access memory directly; in a virtual environment all memory addresses are re-mapped by the virtual machine software, which causes DMA devices to fail.
hˈaɪɚ pɚfˈoːɹməns hˈɑːɹdwɛɹ sˈʌtʃ ɐz ɡɹˈæfɪks kˈɑːɹdz jˈuːs dˌiːˌɛmˈeɪ tʊ ˈæksɛs mˈɛmɚɹi dᵻɹˈɛktli; ɪn ɐ vˈɜːtʃuːəl ɛnvˈaɪɹənmənt ˈɔːl mˈɛmɚɹi ɐdɹˈɛsᵻz ɑːɹ ɹˌiːmˈæpt baɪ ðə vˈɜːtʃuːəl məʃˈiːn sˈɔftwɛɹ, wˌɪtʃ kˈɔːzᵻz dˌiːˌɛmˈeɪ dɪvˈaɪsᵻz tə fˈeɪl.