Messages in this thread | | | Date | Thu, 18 Nov 2021 08:08:54 +0100 | Subject | Re: [PATCH] KVM: MMU: update comment on the number of page role combinations | From | Paolo Bonzini <> |
| |
On 11/17/21 23:25, Sean Christopherson wrote: >> >> Here is a better writeup: >> >> * - invalid shadow pages are not accounted, so the bits are effectively 18 >> * - quadrant will only be used if gpte_is_8_bytes is zero (non-PAE paging); >> * execonly and ad_disabled are only used for nested EPT which has >> * gpte_is_8_bytes=1. Therefore, 2 bits are always unused. >> * - the 4 bits of level are effectively limited to the values 2/3/4/5, >> * as 4k SPs are not tracked (allowed to go unsync). In addition non-PAE >> * paging has exactly one upper level, making level effectively redundant >> * when gpte_is_8_bytes=0. >> * - on top of this, smep_andnot_wp and smap_andnot_wp are only set if cr0_wp=0, >> * therefore these three bits only give rise to 5 possibilities. >> >> FWIW, the full count becomes 6400 unless I screwed up the math. > Which is "in the neighborhood of 2^13":-) >
2^12 if SMM is not counted.
Paolo
| |