linux-kernel - Re: [PATCH v3] vfio/type1: optimize vfio_pin_pages

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250528205802.4afb3a1b.alex.williamson@redhat.com>
Date: Wed, 28 May 2025 20:58:02 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Jason Gunthorpe <jgg@...pe.ca>
Cc: David Hildenbrand <david@...hat.com>, lizhe.67@...edance.com,
 kvm@...r.kernel.org, linux-kernel@...r.kernel.org, muchun.song@...ux.dev
Subject: Re: [PATCH v3] vfio/type1: optimize vfio_pin_pages_remote() for
 huge folio

On Wed, 28 May 2025 21:51:47 -0300
Jason Gunthorpe <jgg@...pe.ca> wrote:

> On Wed, May 28, 2025 at 02:09:41PM -0600, Alex Williamson wrote:
> 
> > To be fair to libvirt, we'd really like libvirt to make use of iommufd
> > whenever it's available, but without feature parity this would break
> > users.    
> 
> If people ask there should be no issue with making API functionality
> discoverable with a query command of some kind. Alot of new stuff is
> already discoverable by invoking an ioctl with bogus arguments and
> checking for EOPNOTSUPP/ENOTTY.
> 
> But most likely P2P will use the same ioctl as memfd so it will not
> work that way.
> 
> So for now libvirt could assume no P2P support in iommufd. A simple
> algorithm would be to look for more than 1 VFIO device. Or add an xml
> "disable P2P" which is a useful thing anyhow.

Hotplug is always a problem if we make assumptions based on device
counts.  Thanks,

Alex