[PATCH v6 3/5] kvm: arm64: New memslot flag to indicate cacheable mapping

[Jason Gunthorpe]

On Sat, May 24, 2025 at 01:39:41AM +0000, ankita at nvidia.com wrote:
> From: Ankit Agrawal <ankita at nvidia.com>
> 
> Introduce a new memslot flag KVM_MEM_ENABLE_CACHEABLE_PFNMAP
> as a tool for userspace to indicate that it expects a particular
> PFN range to be mapped cacheable.
> 
> This will serve as a guide for the KVM to activate the code that
> allows cacheable PFNMAP.
> 
> CC: Oliver Upton <oliver.upton at linux.dev>
> CC: Catalin Marinas <catalin.marinas at arm.com>
> CC: Jason Gunthorpe <jgg at nvidia.com>
> Suggested-by: Marc Zyngier <maz at kernel.org>
> Signed-off-by: Ankit Agrawal <ankita at nvidia.com>
> ---
>  include/uapi/linux/kvm.h | 1 +
>  virt/kvm/kvm_main.c      | 3 ++-
>  2 files changed, 3 insertions(+), 1 deletion(-)

I thought we agreed not to do this? Sean was strongly against it
right?

There is no easy way for VFIO to know to set it, and the kernel will
not allow switching a cachable VMA to non-cachable anyhow.

So all it does is make it harder to create a memslot.

Jason