On Fri, Nov 27, 2020 at 10:14:49AM +0800, Xu, Like wrote: > > OK, but the code here wanted to inspect the guest DS from the host. It > > states this is somehow complicated/expensive. But surely we can at the > > very least map the first guest DS page somewhere so we can at least > > access the control bits without too much magic. > We note that the SDM has a contiguous present memory mapping > assumption about the DS save area and the PEBS buffer area. > > Therefore, we revisit your suggestion here and move it a bit forward: > > When the PEBS is enabled, KVM will cache the following values: > - gva ds_area (kvm msr trap) > - hva1 for "gva ds_area" (walk guest page table) > - hva2 for "gva pebs_buffer_base" via hva1 (walk guest page table) What this [gh]va? Guest/Host Virtual Address? I think you're assuming I know about all this virt crap,.. I don't. > if the "gva ds_area" cache hits, what? > - access PEBS "interrupt threshold" and "Counter Reset[]" via hva1 > - get "gva2 pebs_buffer_base" via __copy_from_user(hva1) But you already had hva2, so what's the point? > if the "gva2 pebs_buffer_base" cache hits, What? > - we get "gva2 pebs_index" via __copy_from_user(hva2), pebs_index is in ds_are, which would be hva1 > - rewrite the guest PEBS records via hva2 and pebs_index > > If any cache misses, setup the cache values via walking tables again. > > I wonder if you would agree with this optimization idea, > we look forward to your confirmation for the next step. I'm utterly confused. I really can't follow.
