(5) as a new security feature of Linux (SED), it supports encryption. The new feature of this time is to support hardware enhanced cache consistency, and the patch developed by Oracle engineers came to Linux 5.10.It is not clear which AMD epyc CPUs support this hardware enhanced cache consistency because it is designed to be used at the CPUID instruction level.
On processors that support this CPUID instruction, consistency between encrypted / unencrypted mappings for the same physical page is guaranteed. Therefore, with this amd hardware enhanced cache consistency, it is not necessary to refresh the page from all CPU caches in the system before changing the C-bit value of the page. In this way, the new feature of avoiding unnecessary cache refresh should be helpful to improve performance.
this patch does not detail any specific advantages and we can not find any public documentation to illustrate this particular SME feature. What is now known is that it has increased