linux-kernel - Re: [PATCH v3 8/8] vfio/pci: Add the support for PCI D3cold state

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20220601173054.GS1343366@nvidia.com>
Date:   Wed, 1 Jun 2022 14:30:54 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     Abhishek Sahu <abhsahu@...dia.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Yishai Hadas <yishaih@...dia.com>,
        Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>,
        Kevin Tian <kevin.tian@...el.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Max Gurtovoy <mgurtovoy@...dia.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v3 8/8] vfio/pci: Add the support for PCI D3cold state

On Wed, Jun 01, 2022 at 10:21:51AM -0600, Alex Williamson wrote:

> Some ioctls clearly cannot occur while the device is in low power, such
> as resets and interrupt control, but even less obvious things like
> getting region info require device access.  Migration also provides a
> channel to device access.  

I wonder what power management means in a case like that.

For the migration drivers they all rely on a PF driver that is not
VFIO, so it should be impossible for power management to cause the PF
to stop working.

I would expect any sane design of power management for a VF to not
cause any harm to the migration driver..

> I'm also still curious how we're going to handle devices that cannot
> return to low power such as the self-refresh mode on the GPU.  We can
> potentially prevent any wake-ups from the vfio device interface, but
> that doesn't preclude a wake-up via an external lspci.  I think we need
> to understand how we're going to handle such devices before we can
> really complete the design.  AIUI, we cannot disable the self-refresh
> sleep mode without imposing unreasonable latency and memory
> requirements on the guest and we cannot retrigger the self-refresh
> low-power mode without non-trivial device specific code.

It begs the question if power management should be something that only
a device-specific drivers should allow?

Jason