Re: [PATCH 1/2] x86: sgx_vepc: extract sgx_vepc_remove_page

Paolo Bonzini
2021-09-13T15:14:59Z

On 13/09/21 16:55, Dave Hansen wrote:
>> By "Windows startup" I mean even after guest reboot.  Because another
>> process could sneak in and steal your EPC pages between a close() and an
>> open(), I'd like to have a way to EREMOVE the pages while keeping them
>> assigned to the specific vEPC instance, i.e.*without* going through
>> sgx_vepc_free_page().
> Oh, so you want fresh EPC state for the guest, but you're concerned that
> the previous guest might have left them in a bad state. The current
> method of getting a new vepc instance (which guarantees fresh state) has
> some other downsides.
>
> Can't another process steal pages via sgxd and reclaim at any time?

vEPC pages never call sgx_mark_page_reclaimable, don't they?

> What's the extra concern here about going through a close()/open()
> cycle? Performance?

Apart from reclaiming, /dev/sgx_vepc might disappear between the first
open() and subsequent ones.

Paolo