linux-kernel - Re: [PATCH AUTOSEL 5.16 36/52] PCI/MSI: Decouple MSI[-X] disable from pcim

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Date:   Mon, 17 Jan 2022 18:08:34 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Nishanth Menon <nm@...com>,
        Michael Kelley <mikelley@...rosoft.com>, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.16 36/52] PCI/MSI: Decouple MSI[-X] disable
 from pcim_release()

On Mon, Jan 17, 2022 at 11:58:37AM -0500, Sasha Levin wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> [ Upstream commit 3f35d2cf9fbc656db82579d849cc69c373b1ad0d ]
> 
> The MSI core will introduce runtime allocation of MSI related data. This
> data will be devres managed and has to be set up before enabling
> PCI/MSI[-X]. This would introduce an ordering issue vs. pcim_release().
> 
> The setup order is:
> 
>    pcim_enable_device()
> 	devres_alloc(pcim_release...);
> 	...
> 	pci_irq_alloc()
> 	  msi_setup_device_data()
> 	     devres_alloc(msi_device_data_release, ...)
> 
> and once the device is released these release functions are invoked in the
> opposite order:
> 
>     msi_device_data_release()
>     ...
>     pcim_release()
>        pci_disable_msi[x]()
> 
> which is obviously wrong, because pci_disable_msi[x]() requires the MSI
> data to be available to tear down the MSI[-X] interrupts.
> 
> Remove the MSI[-X] teardown from pcim_release() and add an explicit action
> to be installed on the attempt of enabling PCI/MSI[-X].
> 
> This allows the MSI core data allocation to be ordered correctly in a
> subsequent step.
> 
> Reported-by: Nishanth Menon <nm@...com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Tested-by: Michael Kelley <mikelley@...rosoft.com>
> Tested-by: Nishanth Menon <nm@...com>
> Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Link: https://lore.kernel.org/r/87tuf9rdoj.ffs@tglx
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/pci/msi.c   | 33 +++++++++++++++++++++++++++++++++
>  drivers/pci/pci.c   |  5 -----
>  include/linux/pci.h |  3 ++-
>  3 files changed, 35 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index d84cf30bb2790..1093f099846eb 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -461,6 +461,31 @@ void pci_restore_msi_state(struct pci_dev *dev)
>  }
>  EXPORT_SYMBOL_GPL(pci_restore_msi_state);
>  
> +static void pcim_msi_release(void *pcidev)
> +{
> +	struct pci_dev *dev = pcidev;
> +
> +	dev->is_msi_managed = false;
> +	pci_free_irq_vectors(dev);
> +}
> +
> +/*
> + * Needs to be separate from pcim_release to prevent an ordering problem
> + * vs. msi_device_data_release() in the MSI core code.
> + */
> +static int pcim_setup_msi_release(struct pci_dev *dev)
> +{
> +	int ret;
> +
> +	if (!pci_is_managed(dev) || dev->is_msi_managed)
> +		return 0;
> +
> +	ret = devm_add_action(&dev->dev, pcim_msi_release, dev);
> +	if (!ret)
> +		dev->is_msi_managed = true;
> +	return ret;
> +}
> +
>  static struct msi_desc *
>  msi_setup_entry(struct pci_dev *dev, int nvec, struct irq_affinity *affd)
>  {
> @@ -1029,6 +1054,10 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
>  	if (nvec > maxvec)
>  		nvec = maxvec;
>  
> +	rc = pcim_setup_msi_release(dev);
> +	if (rc)
> +		return rc;
> +
>  	for (;;) {
>  		if (affd) {
>  			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
> @@ -1072,6 +1101,10 @@ static int __pci_enable_msix_range(struct pci_dev *dev,
>  	if (WARN_ON_ONCE(dev->msix_enabled))
>  		return -EINVAL;
>  
> +	rc = pcim_setup_msi_release(dev);
> +	if (rc)
> +		return rc;
> +
>  	for (;;) {
>  		if (affd) {
>  			nvec = irq_calc_affinity_vectors(minvec, nvec, affd);
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 3d2fb394986a4..f3f606c232a8a 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2024,11 +2024,6 @@ static void pcim_release(struct device *gendev, void *res)
>  	struct pci_devres *this = res;
>  	int i;
>  
> -	if (dev->msi_enabled)
> -		pci_disable_msi(dev);
> -	if (dev->msix_enabled)
> -		pci_disable_msix(dev);
> -
>  	for (i = 0; i < DEVICE_COUNT_RESOURCE; i++)
>  		if (this->region_mask & (1 << i))
>  			pci_release_region(dev, i);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 18a75c8e615cd..e26000404e3c3 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -425,7 +425,8 @@ struct pci_dev {
>  	unsigned int	ats_enabled:1;		/* Address Translation Svc */
>  	unsigned int	pasid_enabled:1;	/* Process Address Space ID */
>  	unsigned int	pri_enabled:1;		/* Page Request Interface */
> -	unsigned int	is_managed:1;
> +	unsigned int	is_managed:1;		/* Managed via devres */
> +	unsigned int	is_msi_managed:1;	/* MSI release via devres installed */
>  	unsigned int	needs_freset:1;		/* Requires fundamental reset */
>  	unsigned int	state_saved:1;
>  	unsigned int	is_physfn:1;
> -- 
> 2.34.1
> 

I do not think this is needed for the stable trees, as it only showed up
in the MSI rework that Thomas added for 5.17-rc1.  So please drop this
from all of the AUTOSEL kernels.

thanks,

greg k-h