On Mon, May 11, 2026 at 11:55:40AM -0400, Michael S. Tsirkin wrote: > On Mon, May 11, 2026 at 11:37:37AM -0400, Gregory Price wrote: > > On Mon, May 11, 2026 at 05:01:55AM -0400, Michael S. Tsirkin wrote: > > > > > +/* > > > + * Sentinel for user_addr: indicates a non-user allocation. > > > + * Cannot use 0 because address 0 is a valid userspace mapping. > > > + */ > > > +#define USER_ADDR_NONE ((unsigned long)-1) > > > > Ehm, hm. Does -1 hold as a non-user address across all architectures? > > > > What about in linear addressing / no VM mode? > > this is used on a fault. I don't think there are any faults then? > But maybe FAULT_ADDR_NONE would be clearer. >
Meh, naming here is less relevant than the sentinel correctness. My only concern is really whether -1 could end up being a valid address in some horrid future timeline and this all going belly up. Is why I asked about whether this is correct on all architectures. > > So the trade off is: > > a) churn the current interface for everyone > > b) add a user_ variant and know people will just get it wrong > > I was also explicitly asked not to proliferate too many new APIs. > Yeah simply spelling it out, not asking for a change. Probably no better way to go about it. ~Gregory
