Messages in this thread | | | Date | Thu, 30 Apr 2020 13:25:16 -0700 | From | "Luck, Tony" <> | Subject | Re: [PATCH v2 0/2] Replace and improve "mcsafe" with copy_safe() |
| |
On Thu, Apr 30, 2020 at 12:50:40PM -0700, Linus Torvalds wrote:
I see your point about the namimg being important. I think Dan's case is indeed "copy from pmem to user" where only options for faulting are #MC on the source addresses, and #PF on the destination.
> The only *fundamental* access would likely be a single read/write > operation, not a copy operation. Think "get_user()" instead of > "copy_from_user()". Even there you get combinatorial explosions with > access sizes, but you can often generate those automatically or with > simple patterns, and then you can build up the copy functions from > that if you really need to.
That's maybe very clean. But it looks like it would be hard to build a high performance interface on top of that primitive. Remember that for Dan's copy 99.999999999367673%[1] of copies will not hit a machine check on the read from pmem.
Dan wants (whatever the function name) to get to a "REP MOVS" with an exception table entry to handle the cases where there is a fault.
-Tony
[1] Likely several more '9's in there
| |