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

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Message-ID: <YexPchGmB/WGQrOE@sashalap>
Date:   Sat, 22 Jan 2022 13:39:46 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.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 06:08:34PM +0100, Greg Kroah-Hartman wrote:
>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.

Dropped, thanks!

-- 
Thanks,
Sasha