Subject: Re: [PATCH v3 1/2] PCI: One more parameter to pci_set_pcie_reset_state()

From: Alex Williamson <[email-masked]>
Date: Mon, 23 Mar 2015 06:40:34 -0600

On Mon, 2015-03-23 at 15:40 +1100, Gavin Shan wrote:
> On Sun, Mar 22, 2015 at 10:06:01PM -0600, Alex Williamson wrote:
> >On Mon, 2015-03-23 at 14:56 +1100, Gavin Shan wrote:
> >> On Sun, Mar 22, 2015 at 09:34:33PM -0600, Alex Williamson wrote:
> >> >On Mon, 2015-03-23 at 14:02 +1100, Gavin Shan wrote:
> >> >> The patch adds one more parameter ("probe") to pci_set_pcie_reset_state(),
> >> >> which allows to check if one particular PCI device can be resetted by the
> >> >> function. The function will be reused to support PCI device specific methods
> >> >> maintained in pci_dev_reset_methods[] in subsequent patch.
> >> >> 
> >> >> Cc: Brian King <[email-masked]>
> >> >> Cc: Frank Haverkamp <[email-masked]>
> >> >> Cc: Ian Munsie <[email-masked]>
> >> >> Signed-off-by: Gavin Shan <[email-masked]>
> >> >> ---
> >> >> v3: Fix arguments of pci_set_pcie_reset_state() in cxl driver
> >> >> v2: Reimplemented based on pci_set_pcie_reset_state()
> >> >> ---
> >> >>  arch/powerpc/kernel/eeh.c       | 14 ++++++++++----
> >> >>  drivers/misc/cxl/pci.c          |  2 +-
> >> >>  drivers/misc/genwqe/card_base.c |  9 +++++++--
> >> >>  drivers/pci/pci.c               | 15 +++++++++------
> >> >>  drivers/scsi/ipr.c              |  5 +++--
> >> >>  include/linux/pci.h             |  5 +++--
> >> >>  6 files changed, 33 insertions(+), 17 deletions(-)
> >> >
> >> >
> >> >Argh, you're trying to make pci_set_pcie_reset_state() compatible with
> >> >pci_dev_specific_reset(), so it can be called via pci_reset_function(),
> >> >but the whole point of the pci_reset_function() interface is to reset a
> >> >*single* function without disturbing anything else.  These patches make
> >> >no effort at all to limit the set of affected devices to a single
> >> >function and take great liberties using PCI_ANY_ID for vendors.  My take
> >> >on the powerpc version of pcibios_set_pcie_reset_state() is that it's
> >> >effectively a slot reset, so why not hook into the
> >> >pci_reset_hotplug_slot() via the hotplug slot ops?  Please also use
> >> >cover letters.  Thanks,
> >> >
> >> 
> >> Yep, that's the point and intention of the patches. pcibios_set_pcie_reset_state()
> >> isn't equal to pci_reset_hotplug_slot(). The later one depends on PCI slot, which
> >> wasn't populated on PowerNV platform yet, but pcibios_set_pcie_reseet_state() doesn't.
> >> 
> >> The patchset depends on improved pcibios_set_pcie_reset_state(), which can be seen
> >> from following linked. With it, we don't affect any PCI devices as the config space
> >> is saved/restored accordingly before/after reset:
> >> 
> >> https://patchwork.ozlabs.org/patch/438598/
> >
> >Sorry, that's wrong.  pci_reset_function() can be called while other
> >devices in the same multifunction package are actively in use.  It
> >doesn't matter that you're saving and restoring the external state of
> >the device, the internal state is lost and operation of the device is
> >interrupted.  That is not how pci_reset_function() is supposed to work.
> >Thanks,
> >
> 
> pcibios_set_pcie_reset_state() applies hot reset on PCI bus, or PCI
> slot fundamental reset essentially. It's potentially affecting multiple
> PCI devices (not functions).
> 
> Yes. It's not safe to call pcibios_set_pcie_reset_state() if some of
> the target functions are actively and in use. I also suspect if it
> works to reset function#0 via pci_reset_function() while function#1
> is actively in use? I guess the caller of pci_reset_function() perhaps
> has to ensure there are no active functions/devices.
> 
> One of the issues the patches try to fix: some of broadcom adapters have
> multile functions, which can't support FLR, AF FLR, PM reset. Also, reset
> on parent PCI bus and the corresponding reset can't be applied because of
> they're multi-function package. In summary, pci_reset_function() doesn't
> work on the adapters. That won't give clean state when passing device from
> host to guest, or return it back to host. Sometimes, the host memory gets
> corrupted when destorying the guest. Occasionally, the patches with improved
> pcibios_set_pcie_reset_state() avoided the issue.
> 
> Some adapters might require fundamental reset on the PCI slot, or hot reset
> on parent bus explicitly, in order to successfully reload its firmware after
> reset.

This is exactly why we have pci_reset_slot() and pci_reset_bus(), so
that the caller can manage the scope of the reset.  You cannot change
the semantics of pci_reset_function() simply because it's convenient for
your implementation.  This series is wrong and should not be applied.
Thanks,

Alex

> >> >> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
> >> >> index daa68a1..cd85c18 100644
> >> >> --- a/arch/powerpc/kernel/eeh.c
> >> >> +++ b/arch/powerpc/kernel/eeh.c
> >> >> @@ -726,11 +726,14 @@ static void *eeh_restore_dev_state(void *data, void *userdata)
> >> >>   * pcibios_set_pcie_slot_reset - Set PCI-E reset state
> >> >>   * @dev: pci device struct
> >> >>   * @state: reset state to enter
> >> >> + * @probe: check if the device can take the reset
> >> >>   *
> >> >>   * Return value:
> >> >>   * 	0 if success
> >> >>   */
> >> >> -int pcibios_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state state)
> >> >> +int pcibios_set_pcie_reset_state(struct pci_dev *dev,
> >> >> +				 enum pcie_reset_state state,
> >> >> +				 int probe)
> >> >>  {
> >> >>  	struct eeh_dev *edev = pci_dev_to_eeh_dev(dev);
> >> >>  	struct eeh_pe *pe = eeh_dev_to_pe(edev);
> >> >> @@ -738,9 +741,12 @@ int pcibios_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state stat
> >> >>  	if (!pe) {
> >> >>  		pr_err("%s: No PE found on PCI device %s\n",
> >> >>  			__func__, pci_name(dev));
> >> >> -		return -EINVAL;
> >> >> +		return -ENOTTY;
> >> >>  	}
> >> >>  
> >> >> +	if (probe)
> >> >> +		return 0;
> >> >> +
> >> >>  	switch (state) {
> >> >>  	case pcie_deassert_reset:
> >> >>  		eeh_ops->reset(pe, EEH_RESET_DEACTIVATE);
> >> >> @@ -762,8 +768,8 @@ int pcibios_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state stat
> >> >>  		break;
> >> >>  	default:
> >> >>  		eeh_pe_state_clear(pe, EEH_PE_CFG_BLOCKED);
> >> >> -		return -EINVAL;
> >> >> -	};
> >> >> +		return -ENOTTY;
> >> >> +	}
> >> >>  
> >> >>  	return 0;
> >> >>  }
> >> >> diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
> >> >> index 1ef0164..3a87bfc 100644
> >> >> --- a/drivers/misc/cxl/pci.c
> >> >> +++ b/drivers/misc/cxl/pci.c
> >> >> @@ -789,7 +789,7 @@ int cxl_reset(struct cxl *adapter)
> >> >>  	/* pcie_warm_reset requests a fundamental pci reset which includes a
> >> >>  	 * PERST assert/deassert.  PERST triggers a loading of the image
> >> >>  	 * if "user" or "factory" is selected in sysfs */
> >> >> -	if ((rc = pci_set_pcie_reset_state(dev, pcie_warm_reset))) {
> >> >> +	if ((rc = pci_set_pcie_reset_state(dev, pcie_warm_reset, 0))) {
> >> >>  		dev_err(&dev->dev, "cxl: pcie_warm_reset failed\n");
> >> >>  		return rc;
> >> >>  	}
> >> >> diff --git a/drivers/misc/genwqe/card_base.c b/drivers/misc/genwqe/card_base.c
> >> >> index 4cf8f82..4871f69 100644
> >> >> --- a/drivers/misc/genwqe/card_base.c
> >> >> +++ b/drivers/misc/genwqe/card_base.c
> >> >> @@ -782,17 +782,22 @@ static int genwqe_pci_fundamental_reset(struct pci_dev *pci_dev)
> >> >>  {
> >> >>  	int rc;
> >> >>  
> >> >> +	/* Probe if the device can take the reset */
> >> >> +	rc = pci_set_pcie_reset_state(pci_dev, pcie_warm_reset, 1);
> >> >> +	if (rc)
> >> >> +		return rc;
> >> >> +
> >> >>  	/*
> >> >>  	 * lock pci config space access from userspace,
> >> >>  	 * save state and issue PCIe fundamental reset
> >> >>  	 */
> >> >>  	pci_cfg_access_lock(pci_dev);
> >> >>  	pci_save_state(pci_dev);
> >> >> -	rc = pci_set_pcie_reset_state(pci_dev, pcie_warm_reset);
> >> >> +	rc = pci_set_pcie_reset_state(pci_dev, pcie_warm_reset, 0);
> >> >>  	if (!rc) {
> >> >>  		/* keep PCIe reset asserted for 250ms */
> >> >>  		msleep(250);
> >> >> -		pci_set_pcie_reset_state(pci_dev, pcie_deassert_reset);
> >> >> +		pci_set_pcie_reset_state(pci_dev, pcie_deassert_reset, 0);
> >> >>  		/* Wait for 2s to reload flash and train the link */
> >> >>  		msleep(2000);
> >> >>  	}
> >> >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> >> >> index 81f06e8..8581a5f 100644
> >> >> --- a/drivers/pci/pci.c
> >> >> +++ b/drivers/pci/pci.c
> >> >> @@ -1558,28 +1558,31 @@ EXPORT_SYMBOL(pci_disable_device);
> >> >>   * pcibios_set_pcie_reset_state - set reset state for device dev
> >> >>   * @dev: the PCIe device reset
> >> >>   * @state: Reset state to enter into
> >> >> - *
> >> >> + * @probe: Check if the device can take the reset
> >> >>   *
> >> >>   * Sets the PCIe reset state for the device. This is the default
> >> >>   * implementation. Architecture implementations can override this.
> >> >>   */
> >> >>  int __weak pcibios_set_pcie_reset_state(struct pci_dev *dev,
> >> >> -					enum pcie_reset_state state)
> >> >> +					enum pcie_reset_state state,
> >> >> +					int probe)
> >> >>  {
> >> >> -	return -EINVAL;
> >> >> +	return -ENOTTY;
> >> >>  }
> >> >>  
> >> >>  /**
> >> >>   * pci_set_pcie_reset_state - set reset state for device dev
> >> >>   * @dev: the PCIe device reset
> >> >>   * @state: Reset state to enter into
> >> >> - *
> >> >> + * @probe: Check if the device can take the reset
> >> >>   *
> >> >>   * Sets the PCI reset state for the device.
> >> >>   */
> >> >> -int pci_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state state)
> >> >> +int pci_set_pcie_reset_state(struct pci_dev *dev,
> >> >> +			     enum pcie_reset_state state,
> >> >> +			     int probe)
> >> >>  {
> >> >> -	return pcibios_set_pcie_reset_state(dev, state);
> >> >> +	return pcibios_set_pcie_reset_state(dev, state, probe);
> >> >>  }
> >> >>  EXPORT_SYMBOL_GPL(pci_set_pcie_reset_state);
> >> >>  
> >> >> diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
> >> >> index 9219953..89026f4 100644
> >> >> --- a/drivers/scsi/ipr.c
> >> >> +++ b/drivers/scsi/ipr.c
> >> >> @@ -8317,7 +8317,8 @@ static int ipr_reset_start_bist(struct ipr_cmnd *ipr_cmd)
> >> >>  static int ipr_reset_slot_reset_done(struct ipr_cmnd *ipr_cmd)
> >> >>  {
> >> >>  	ENTER;
> >> >> -	pci_set_pcie_reset_state(ipr_cmd->ioa_cfg->pdev, pcie_deassert_reset);
> >> >> +	pci_set_pcie_reset_state(ipr_cmd->ioa_cfg->pdev,
> >> >> +				 pcie_deassert_reset, 0);
> >> >>  	ipr_cmd->job_step = ipr_reset_bist_done;
> >> >>  	ipr_reset_start_timer(ipr_cmd, IPR_WAIT_FOR_BIST_TIMEOUT);
> >> >>  	LEAVE;
> >> >> @@ -8339,7 +8340,7 @@ static int ipr_reset_slot_reset(struct ipr_cmnd *ipr_cmd)
> >> >>  	struct pci_dev *pdev = ioa_cfg->pdev;
> >> >>  
> >> >>  	ENTER;
> >> >> -	pci_set_pcie_reset_state(pdev, pcie_warm_reset);
> >> >> +	pci_set_pcie_reset_state(pdev, pcie_warm_reset, 0);
> >> >>  	ipr_cmd->job_step = ipr_reset_slot_reset_done;
> >> >>  	ipr_reset_start_timer(ipr_cmd, IPR_PCI_RESET_TIMEOUT);
> >> >>  	LEAVE;
> >> >> diff --git a/include/linux/pci.h b/include/linux/pci.h
> >> >> index 4e1f17d..052ac63 100644
> >> >> --- a/include/linux/pci.h
> >> >> +++ b/include/linux/pci.h
> >> >> @@ -960,7 +960,8 @@ extern unsigned int pcibios_max_latency;
> >> >>  void pci_set_master(struct pci_dev *dev);
> >> >>  void pci_clear_master(struct pci_dev *dev);
> >> >>  
> >> >> -int pci_set_pcie_reset_state(struct pci_dev *dev, enum pcie_reset_state state);
> >> >> +int pci_set_pcie_reset_state(struct pci_dev *dev,
> >> >> +			     enum pcie_reset_state state, int probe);
> >> >>  int pci_set_cacheline_size(struct pci_dev *dev);
> >> >>  #define HAVE_PCI_SET_MWI
> >> >>  int __must_check pci_set_mwi(struct pci_dev *dev);
> >> >> @@ -1648,7 +1649,7 @@ extern unsigned long pci_hotplug_mem_size;
> >> >>  void pcibios_disable_device(struct pci_dev *dev);
> >> >>  void pcibios_set_master(struct pci_dev *dev);
> >> >>  int pcibios_set_pcie_reset_state(struct pci_dev *dev,
> >> >> -				 enum pcie_reset_state state);
> >> >> +				 enum pcie_reset_state state, int probe);
> >> >>  int pcibios_add_device(struct pci_dev *dev);
> >> >>  void pcibios_release_device(struct pci_dev *dev);
> >> >>  void pcibios_penalize_isa_irq(int irq, int active);
> >> >
> >> >
> >> >
> >> 
> >
> >
> >
>