On Wed, May 18, 2022, Vitaly Kuznetsov wrote: > Sean Christopherson <seanjc@xxxxxxxxxx> writes: > > > On Wed, May 18, 2022, Vitaly Kuznetsov wrote: > >> Maxim Levitsky <mlevitsk@xxxxxxxxxx> writes: > >> > Or if using kfifo, then it can contain plain u64 items, which is even more natural. > >> > > >> > >> In the next version I switch to fifo and get rid of 'flush_all' entries > >> but instead of a boolean I use a 'magic' value of '-1' in GVA. This way > >> we don't need to synchronize with the reader and add any special > >> handling for the flag. > > > > Isn't -1 theoretically possible? Or is wrapping not allowed? E.g. requesting a > > flush for address=0xfffffffffffff000, count = 0xfff will yield -1 and doesn't > > create any illegal addresses in the process. > > > > Such an error would just lead to KVM flushing the whole guest address > space instead of flushing 4096 pages starting with 0xfffffffffffff000 > but over-flushing is always architecturally correct, isn't it? Oh, duh. Yeah, flushing everything is totally ok. Maybe just add a comment above the #define for the magic value calling out that corner case and why it's ok?
