ACTIVE - Kernel with migrating threads as IPC https://metanimi.dy.fi/cgit/kmi/atom?h=master 2024-07-09T14:35:56Z 2024-07-09T14:35:56Z Kimplul kimi.h.kuparinen@gmail.com 2024-07-09T14:35:56Z urn:sha1:298636079d912d0936f8156a609fe74b839c547b + User has to 'free' the 0 page before it becomes accessible to mapping. Probably worth noting that this is likely VERY niche and mainly concerns stuff like certain kinds of emulators that I'm still eons from implementing, but still. Unbacked pages can also be useful for some kinds of notifications, like 'if someone writes to this page, please report it to me with this ID' or whatever, I remember seeing some discussion about it somewhere but that's also not really relevant for the moment. Most significantly, at least with the current design, after the null page is freed it becomes available for use to regular req_mem() calls, so users should probably using locks around memory requests. That's probably a good idea anyway as internally the kernal has to lock the virtual memory, and without a scheduler it might cause threads to spin for a while in the kernel which is rather bad. 2024-07-07T04:00:43Z Kimplul kimi.h.kuparinen@gmail.com 2024-07-07T04:00:43Z urn:sha1:122374c362ba8bb9082385da3c82e264ab594f15 + Had some minor issues with a wraparound of size_t that effectively meant that some regions were allocated twice. Also, booting should be a bit more reliable now, turned out that the previous iteration of the booting was just accidentally working due to the kernel being placed 'close enough' in RAM to where it was linked to. Fixed by allocating a vmem of O1 that maps the kernel to a 2MiB boundary at boot, pretty nifty. 2024-07-06T18:07:35Z Kimplul kimi.h.kuparinen@gmail.com 2024-07-06T18:07:35Z urn:sha1:70afa4184544d244d804713fdee5836f4f20a9fe 2024-07-06T16:31:13Z Kimplul kimi.h.kuparinen@gmail.com 2024-07-06T16:31:13Z urn:sha1:f810f1583725b84d3538adfe2aab6dea00f5ae87 2023-10-09T13:15:06Z Kimplul kimi.h.kuparinen@gmail.com 2023-10-09T11:57:18Z urn:sha1:9c9d589ea310f1290e4d6d2019fc8b51d9a86e42 + Fairly considerable speedup, as we don't have to look up the rpc pte every time separately, instead cacheing them. Adds an architecture specific limitation to total rpc stack size, though. 2023-06-04T12:13:43Z Kimplul kimi.h.kuparinen@gmail.com 2023-06-04T12:13:43Z urn:sha1:3dbd8c34176312b0bd3aba2309d284ac83181411 + Make 8250 serial driver more generic + Still TODO: write a tutorial on how to boot on the visionfive2 2023-05-11T19:55:31Z Kimplul kimi.h.kuparinen@gmail.com 2023-05-11T19:55:31Z urn:sha1:27ffa747f36aee9c1d5bbc61395a078238366070 + Both kind of go hand in hand, made sense to do both at the same time. Some parts feel slightly hacky, the loader works by placing everything on the stack and avoiding global values. Still, seems to work? 2023-05-01T19:02:49Z Kimplul kimi.h.kuparinen@gmail.com 2023-05-01T19:02:49Z urn:sha1:05d4244f68e35c1bef6488292bf9730df3636fd9 2023-04-30T14:06:02Z Kimplul kimi.h.kuparinen@gmail.com 2023-04-30T14:06:02Z urn:sha1:ea5ebe0809fb31b9f125ac0689f706cc5f3f078f 2022-11-13T05:28:52Z Kimplul kimi.h.kuparinen@gmail.com 2022-11-13T05:28:52Z urn:sha1:b36e3b83b402ee054c319f0472b16a2bd64bba7e + The secret is using gravestones. I'll have to write up full documentation for the feature but essentially riscv lets us encode whatever we want into page table entries, as long as they're not active. We use this to encode highest user address that is not a zero, in that all entries in the top level are either active or gravestones. When an active entry is removed, it is either a gravestone (if there are other active entries above it) or it starts a cascade of removing entries that have been previously removed Slight runtime overhead to page mapping, pretty major advantage in rpc calls. Feature will need to be tested more thorougly, and the init program is sort of a best scenario with just one top level userspace page table entry active at a time, leading to incredibly fast context switches. Current implementation limits a process' max virtual memory to 248 GiB (in Sv39), but I don't think the missing 8 GiB is that big of a deal.