> On Jun 17, 2019, at 11:07 AM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > > On 6/17/19 9:53 AM, Nadav Amit wrote: >>>> For anyone following along at home, I'm going to go off into crazy >>>> per-cpu-pgds speculation mode now... Feel free to stop reading now. :) >>>> >>>> But, I was thinking we could get away with not doing this on _every_ >>>> context switch at least. For instance, couldn't 'struct tlb_context' >>>> have PGD pointer (or two with PTI) in addition to the TLB info? That >>>> way we only do the copying when we change the context. Or does that tie >>>> the implementation up too much with PCIDs? >>> Hmm, that seems entirely reasonable. I think the nasty bit would be >>> figuring out all the interactions with PV TLB flushing. PV TLB >>> flushes already don't play so well with PCID tracking, and this will >>> make it worse. We probably need to rewrite all that code regardless. >> How is PCID (as you implemented) related to TLB flushing of kernel (not >> user) PTEs? These kernel PTEs would be global, so they would be invalidated >> from all the address-spaces using INVLPG, I presume. No? > > The idea is that you have a per-cpu address space. Certain kernel > virtual addresses would map to different physical address based on where > you are running. Each of the physical addresses would be "owned" by a > single CPU and would, by convention, never use a PGD that mapped an > address unless that CPU that "owned" it. > > In that case, you never really invalidate those addresses. I understand, but as I see it, this is not related directly to PCIDs.
