Re: [PATCH v3 3/3] vfio-pci: Invalidate mmaps and block MMIO access on disabled memory

From: Jason Gunthorpe
Date: Mon May 25 2020 - 08:26:11 EST

On Sat, May 23, 2020 at 07:52:57PM -0400, Peter Xu wrote:

> For what I understand now, IMHO we should still need all those handlings of
> FAULT_FLAG_RETRY_NOWAIT like in the initial version. E.g., IIUC KVM gup will
> try with FOLL_NOWAIT when async is allowed, before the complete slow path. I'm
> not sure what would be the side effect of that if fault() blocked it. E.g.,
> the caller could be in an atomic context.

AFAICT FAULT_FLAG_RETRY_NOWAIT only impacts what happens when
VM_FAULT_RETRY is returned, which this doesn't do?

It is not a generic 'do not sleep'

Do you know different?