[RFC PATCH 2/7] x86/sci: add core implementation for system call isolation

[James Bottomley]

On Fri, 2019-04-26 at 07:46 -0700, Dave Hansen wrote:
> On 4/25/19 2:45 PM, Mike Rapoport wrote:
> > After the isolated system call finishes, the mappings created
> > during its execution are cleared.
> 
> Yikes.  I guess that stops someone from calling write() a bunch of
> times on every filesystem using every block device driver and all the
> DM code to get a lot of code/data faulted in.  But, it also means not
> even long-running processes will ever have a chance of behaving
> anything close to normally.
> 
> Is this something you think can be rectified or is there something
> fundamental that would keep SCI page tables from being cached across
> different invocations of the same syscall?

There is some work being done to look at pre-populating the isolated
address space with the expected execution footprint of the system call,
yes.  It lessens the ROP gadget protection slightly because you might
find a gadget in the pre-populated code, but it solves a lot of the
overhead problem.

James