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

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Message-ID: <aEl8J3kv6HAcAkUp@gcabiddu-mobl.ger.corp.intel.com>
Date: Wed, 11 Jun 2025 13:52:55 +0100
From: "Cabiddu, Giovanni" <giovanni.cabiddu@...el.com>
To: Mario Limonciello <superm1@...nel.org>, <bhelgaas@...gle.com>,
	<alex.williamson@...hat.com>
CC: <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

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,

-- 
Giovanni