On 29/07/21 05:00, Yu Zhang wrote:
I have a few questions about these unnecessary tear-downs during boot:
1. How many teardowns did you observe, and how many different roles
did they represent? Just thrashing between two roles, or 12 different
roles?
I saw 106 reloadings of the root TDP. Among them, 14 are caused by memslot
changes. Remaining ones are caused by the context reset from CR0/CR4/EFER
changes(85 for CR0 changes).
Possibly because CR0/CR4/EFER are changed multiple times on SMM entry
(to go from real mode to protected mode to 32-bit to 64-bit)? But most
of those page tables should be very very small; they probably have only
one page per level. The SMM page tables are very small too, the only
one that is really expensive to rebuild is the main non-SMM EPT.
Paolo
