It's an interesting question. First of all, I would note that much of The Odyssey was itself based on heroic myths which were, in a way, larger than Homer himself (we should not assume that Homer invented the stories of the Trojan War or Odysseus or the myths surrounding them). For example, when it comes to Odysseus's journeys from Ithaca as well as the sufferings of other heroes which you hear about in the narrative, we should recognize that, at least to some part, these stories are actually larger than Homer himself.
Now, as far as Homer's own attitude towards warfare goes: that's a tricky, and possibly ambiguous question, because as a previous contributor has already pointed out, there is a lot in Homer which does seem critical to war. There was earlier mentioned Odysseus's encounter with Achilles in the Underworld, from which we get a sense that one's heroics in life cannot in any way soothe the misery of death. Yet, consider the words that follow this:
"But come, tell me the news about my gallant son. / Did he make his way to the wars, / did the boy become a champion - yes or no? / Tell me of noble Peleus, and word you've heard -/ still holding pride of place among his Myrmidon hordes, / or do they despise the man in Hellas and in Phthia/ because old age has lamed his arms and legs?" (The Odyssey, trans. Robert Fagles, Penguin Classics Edition, 1996.)
Ultimately, I'd say Homer's treatment of this theme is actually quite complicated within The Odyssey, because Homer does seem to be approaching the theme of war and violence from two very different perspectives. On the one hand, he is well aware that war creates suffering and large scale death, and the ultimate aim of his journey remains to return home. On the other hand, The Odyssey does tend to revel in feats of martial valor, strength of arms, and its hero's own heroic exploits. We see both these qualities side-by-side early on in Odysseus's own storytelling. In the beginning of Book 9, he describes the attack on the city of Ismarus, portraying the sack and plundering of the city as a triumph, but read a little further, and you'll see the Cicones returning in greater numbers, driving them off by force, leaving them "glad to escape our death/ yet sick at heart for the dear companions we had lost." (Trans. Fagles) Additionally, consider the famous scene near the end of The Odyssey, where Odysseus slaughters the Suitors, and think about how this scene is portrayed in the poem. More than anything else, I'd suggest that, within The Odyssey, Homer tends to celebrate heroism and military achievement, while simultaneously recognizing its very great cost.