[HN Gopher] The trouble with 64-bit DMA in Linux ___________________________________________________________________ The trouble with 64-bit DMA in Linux Author : chmaynard Score : 10 points Date : 2022-08-11 15:45 UTC (1 days ago) (HTM) web link (lwn.net) (TXT) w3m dump (lwn.net) | jasoneckert wrote: | "One of the core rules of kernel development is that good things | rarely result from breaking Linus Torvalds's machine..." sums up | this post beautifully. | wrs wrote: | This is a tangent, but I was reminded of early Macintosh days, | where the 68000 processor in the original Mac hardware only paid | attention to the lower 24 bits of addresses, and only the lower | 22 were actually connected to memory. The heap manager used the | upper bits of pointers as a convenient place to store flags, and | didn't bother zeroing them on dereference because they were | ignored anyway. | | The release of the 68020 and Macs with more RAM resulted in the | need for a whole transition to "32-bit clean" system and apps | that took a while. I also seem to recall something about early | versions of Microsoft Mac apps being limited to the lower | megabyte of RAM for a similar reason. | chmaynard wrote: | See https://lwn.net/SubscriberLink/904210/46bbced99963b245/ | sophacles wrote: | @dang - Can you edit the top link to this subscriber link so | folks with out an account at lwn don't have to search the | comments please? | | Also for everyone else - just a reminder, LWN is a great | resource and is funded through subscriptions. Personally, I've | found the information on this site to be extremely helpful to | understanding how the kernel works - to the point that multiple | products I've built were only really doable because of LWN | articles explaining the subsystem I'm working with (namespaces, | io_uring, etc are all are the topic of fantastic articles | there). A personal subscription is extremely affordable and | very much worth it. They have corporate site license | subscriptions too. | tuckerpo wrote: | Thanks. ___________________________________________________________________ (page generated 2022-08-12 23:00 UTC)