On 14/08/19 09:03, Yang Weijiang wrote: > EPT-Based Sub-Page write Protection(SPP)is a HW capability which allows > Virtual Machine Monitor(VMM) to specify write-permission for guest > physical memory at a sub-page(128 byte) granularity. When this > capability is enabled, the CPU enforces write-access check for sub-pages > within a 4KB page. > > The feature is targeted to provide fine-grained memory protection for > usages such as device virtualization, memory check-point and VM > introspection etc. > > SPP is active when the "sub-page write protection" (bit 23) is 1 in > Secondary VM-Execution Controls. The feature is backed with a Sub-Page > Permission Table(SPPT), SPPT is referenced via a 64-bit control field > called Sub-Page Permission Table Pointer (SPPTP) which contains a > 4K-aligned physical address. > > Right now, only 4KB physical pages are supported for SPP. To enable SPP > for certain physical page, we need to first make the physical page > write-protected, then set bit 61 of the corresponding EPT leaf entry. > While HW walks EPT, if bit 61 is set, it traverses SPPT with the guset > physical address to find out the sub-page permissions at the leaf entry. > If the corresponding bit is set, write to sub-page is permitted, > otherwise, SPP induced EPT violation is generated. Still no testcases? Paolo
