On 20/09/19 14:18, Peter Xu wrote: > (1) memory region aliasing, hence multiple GPAs can point to the same > HVA/HPA so we need to clear the memslot dirty bits on all the > mapped GPAs, and, > > (2) large log_clear() request which can cover more than one valid > kvm memslots. Note that in this case, the mem slots can really > be having different HVAs so imho it should be a different issue > comparing to (1) > > The commit message says it's solving problem (1). However for what I > understand, we are actually doing well on issue (1) because in > memory_region_clear_dirty_bitmap() we iterate over all the flat views > so that we should have caught all the aliasing memory regions if there > are any.
There could be two addresses pointing to the same HVA *in the same flatview*. See for example 0xe0000..0xfffff and 0xffffe000..0xffffffff when a PC guest is started. In this particular case 0xffffe000..0xffffffff is ROM, so it's not an issue, but in other cases it may > However this patch should perfectly fix problem (2). Am I right? I hadn't thought of problem (2). I guess without Igor's work for s390 it does not exist? But yes, it fixes it just the same. Paolo
