linux-kernel - Re: [PATCH v2] PCI: Explicitly put devices into D0 when initializing

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Message-ID: <aEmS+OQL7IbjdwKs@gcabiddu-mobl.ger.corp.intel.com>
Date: Wed, 11 Jun 2025 15:30:16 +0100
From: "Cabiddu, Giovanni" <giovanni.cabiddu@...el.com>
To: Mario Limonciello <superm1@...nel.org>
CC: <bhelgaas@...gle.com>, <alex.williamson@...hat.com>,
	<mario.limonciello@....com>, <rafael.j.wysocki@...el.com>,
	<huang.ying.caritas@...il.com>, <stern@...land.harvard.edu>,
	<linux-pci@...r.kernel.org>, <mike.ximing.chen@...el.com>,
	<ahsan.atta@...el.com>, <suman.kumar.chakraborty@...el.com>,
	<kvm@...r.kernel.org>, <linux-crypto@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] PCI: Explicitly put devices into D0 when initializing
 - Bug report

On Wed, Jun 11, 2025 at 06:50:59AM -0700, Mario Limonciello wrote:
> On 6/11/2025 5:52 AM, Cabiddu, Giovanni wrote:
> > Hi Mario, Bjorn and Alex,
> > 
> > On Wed, Apr 23, 2025 at 11:31:32PM -0500, Mario Limonciello wrote:
> > > From: Mario Limonciello <mario.limonciello@....com>
> > > 
> > > AMD BIOS team has root caused an issue that NVME storage failed to come
> > > back from suspend to a lack of a call to _REG when NVME device was probed.
> > > 
> > > commit 112a7f9c8edbf ("PCI/ACPI: Call _REG when transitioning D-states")
> > > added support for calling _REG when transitioning D-states, but this only
> > > works if the device actually "transitions" D-states.
> > > 
> > > commit 967577b062417 ("PCI/PM: Keep runtime PM enabled for unbound PCI
> > > devices") added support for runtime PM on PCI devices, but never actually
> > > 'explicitly' sets the device to D0.
> > > 
> > > To make sure that devices are in D0 and that platform methods such as
> > > _REG are called, explicitly set all devices into D0 during initialization.
> > > 
> > > Fixes: 967577b062417 ("PCI/PM: Keep runtime PM enabled for unbound PCI devices")
> > > Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> > > ---
> > Through a bisect, we identified that this patch, in v6.16-rc1,
> > introduces a regression on vfio-pci across all Intel QuickAssist (QAT)
> > devices. Specifically, the ioctl VFIO_GROUP_GET_DEVICE_FD call fails
> > with -EACCES.
> > 
> > Upon further investigation, the -EACCES appears to originate from the
> > rpm_resume() function, which is called by pm_runtime_resume_and_get()
> > within vfio_pci_core_enable(). Here is the exact call trace:
> > 
> >      drivers/base/power/runtime.c: rpm_resume()
> >      drivers/base/power/runtime.c: __pm_runtime_resume()
> >      include/linux/pm_runtime.h: pm_runtime_resume_and_get()
> >      drivers/vfio/pci/vfio_pci_core.c: vfio_pci_core_enable()
> >      drivers/vfio/pci/vfio_pci.c: vfio_pci_open_device()
> >      drivers/vfio/vfio_main.c: device->ops->open_device()
> >      drivers/vfio/vfio_main.c: vfio_df_device_first_open()
> >      drivers/vfio/vfio_main.c: vfio_df_open()
> >      drivers/vfio/group.c: vfio_df_group_open()
> >      drivers/vfio/group.c: vfio_device_open_file()
> >      drivers/vfio/group.c: vfio_group_ioctl_get_device_fd()
> >      drivers/vfio/group.c: vfio_group_fops_unl_ioctl(..., VFIO_GROUP_GET_DEVICE_FD, ...)
> > 
> > Is this a known issue that affects other devices? Is there any ongoing
> > discussion or fix in progress?
> > 
> > Thanks,
> > 
> 
> This is the first I've heard about an issue with that patch.
> 
> Does setting the VFIO parameter disable_idle_d3 help?

It does, ... a bit. With disable_idle_d3=1 the ioctl() is successful, but a
subsequent read on that file descriptor fails with -EIO.

    ioctl(5, VFIO_GROUP_GET_DEVICE_FD, 0x7ffd2b38abf0) = 6
    pread64(6, 0x7ffd2b38ab06, 2, 7696581394436) = -1 EIO (Input/output error)

> 
> If so; this feels like an imbalance of runtime PM calls in the VFIO stack
> that this patch exposed.
> 
> Alex, any ideas?
> 

Regards,

-- 
Giovanni