On Tue 31 Jan 2017 05:41:23 PM CET, Eric Blake <ebl...@redhat.com> wrote:
>>> Ideally, it would be nice to fix the block layer to allow larger >>> requests (since we already have code to auto-fragment down to device >>> limits, we should be able to rely on that code instead of having to >>> duplicate artificial constraints everywhere else in the tree). But >>> that's a bigger task, and this is a good patch in the interim. >> >> Related question: what's the largest request than a guest can >> theoretically submit? > > off_t supports up to 2^63 (not 2^64, because it is a signed type). > Ideally, we should be constrained only by the disk size (as no one > actually has 2^63 bytes of storage available), by using uint64_t > offset AND length in all our APIs; but right now, we still have a lot > of 32-bit length issues, and often signed length limiting us to 2^31 > depending on the API. My question was more like: what happens if the guest submits a request with the maximum possible size? Does QEMU handle that correctly? Berto
