Re: [LSF/MM TOPIC] Impact on core mm from new hardware features

[Matthew Wilcox <willy@infradead.org>]

On Tue, Jun 22, 2021 at 07:55:48AM -0700, Dave Hansen wrote:
> There should be enough x86 folks around, but I'd love to hear from the
> ARM and powerpc people as well.

Possibly also s390.  eg f28d43636d6f seems very similar to one of the
things Intel wants.

> Here are a few mostly Intel-specific things I'd like to discuss.
> However, all of these either have analogs on other architectures or are
> implemented by other x86 vendors.
> 
>  * Shadow Stacks - requires new Copy-on-Read memory type.  Creates
>    application mappings which are effectively PROT_NONE, but which are
>    implicitly accessible by the hardware.
>  * Linear Address Masking (LAM) - Similar to ARM's Top Byte Ignore
>    (TBI).  Repurpose some virtual address bits to store metadata.  Intel
>    implementation can sacrifice user address space.  Offloads some of
>    the work the compiler does in ASAN implementations.
>  * Supervisor Protection Keys - Extends Memory Protection Keys (pkeys)
>    to kernel mappings.
>  * TDX - VMs that don't trust the hypervisor.  Requires unmapping guest
>    memory from userspace and possibly the host kernel.