Commit fb51ccbf authored by Jan Kiszka's avatar Jan Kiszka Committed by Jesse Barnes
Browse files

PCI: Rework config space blocking services 



pci_block_user_cfg_access was designed for the use case that a single
context, the IPR driver, temporarily delays user space accesses to the
config space via sysfs. This assumption became invalid by the time
pci_dev_reset was added as locking instance. Today, if you run two loops
in parallel that reset the same device via sysfs, you end up with a
kernel BUG as pci_block_user_cfg_access detect the broken assumption.

This reworks the pci_block_user_cfg_access to a sleeping service
pci_cfg_access_lock and an atomic-compatible variant called
pci_cfg_access_trylock. The former not only blocks user space access as
before but also waits if access was already locked. The latter service
just returns false in this case, allowing the caller to resolve the
conflict instead of raising a BUG.

Adaptions of the ipr driver were originally written by Brian King.

Acked-by: default avatarBrian King <brking@linux.vnet.ibm.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
parent ae5cd864

drivers/pci/access.c

+48 −26
Original line number Diff line number Diff line
@@ -127,20 +127,20 @@ EXPORT_SYMBOL(pci_write_vpd); 
 * We have a bit per device to indicate it's blocked and a global wait queue

 * for callers to sleep on until devices are unblocked.

 */

static DECLARE_WAIT_QUEUE_HEAD(pci_ucfg_wait);

static DECLARE_WAIT_QUEUE_HEAD(pci_cfg_wait);



static noinline void pci_wait_ucfg(struct pci_dev *dev)

static noinline void pci_wait_cfg(struct pci_dev *dev)

{

	DECLARE_WAITQUEUE(wait, current);



	__add_wait_queue(&pci_ucfg_wait, &wait);

	__add_wait_queue(&pci_cfg_wait, &wait);

	do {

		set_current_state(TASK_UNINTERRUPTIBLE);

		raw_spin_unlock_irq(&pci_lock);

		schedule();

		raw_spin_lock_irq(&pci_lock);

	} while (dev->block_ucfg_access);

	__remove_wait_queue(&pci_ucfg_wait, &wait);

	} while (dev->block_cfg_access);

	__remove_wait_queue(&pci_cfg_wait, &wait);

}



/* Returns 0 on success, negative values indicate error. */
@@ -153,7 +153,8 @@ int pci_user_read_config_##size \ 
	if (PCI_##size##_BAD)						\

		return -EINVAL;						\

	raw_spin_lock_irq(&pci_lock);				\

	if (unlikely(dev->block_ucfg_access)) pci_wait_ucfg(dev);	\

	if (unlikely(dev->block_cfg_access))				\

		pci_wait_cfg(dev);					\

	ret = dev->bus->ops->read(dev->bus, dev->devfn,			\

					pos, sizeof(type), &data);	\

	raw_spin_unlock_irq(&pci_lock);				\
@@ -172,7 +173,8 @@ int pci_user_write_config_##size \ 
	if (PCI_##size##_BAD)						\

		return -EINVAL;						\

	raw_spin_lock_irq(&pci_lock);				\

	if (unlikely(dev->block_ucfg_access)) pci_wait_ucfg(dev);	\

	if (unlikely(dev->block_cfg_access))				\

		pci_wait_cfg(dev);					\

	ret = dev->bus->ops->write(dev->bus, dev->devfn,		\

					pos, sizeof(type), val);	\

	raw_spin_unlock_irq(&pci_lock);				\
@@ -401,36 +403,56 @@ int pci_vpd_truncate(struct pci_dev *dev, size_t size) 
EXPORT_SYMBOL(pci_vpd_truncate);



/**

 * pci_block_user_cfg_access - Block userspace PCI config reads/writes

 * pci_cfg_access_lock - Lock PCI config reads/writes

 * @dev:	pci device struct

 *

 * When user access is blocked, any reads or writes to config space will

 * sleep until access is unblocked again.  We don't allow nesting of

 * block/unblock calls.

 * When access is locked, any userspace reads or writes to config

 * space and concurrent lock requests will sleep until access is

 * allowed via pci_cfg_access_unlocked again.

 */

void pci_block_user_cfg_access(struct pci_dev *dev)

void pci_cfg_access_lock(struct pci_dev *dev)

{

	might_sleep();



	raw_spin_lock_irq(&pci_lock);

	if (dev->block_cfg_access)

		pci_wait_cfg(dev);

	dev->block_cfg_access = 1;

	raw_spin_unlock_irq(&pci_lock);

}

EXPORT_SYMBOL_GPL(pci_cfg_access_lock);



/**

 * pci_cfg_access_trylock - try to lock PCI config reads/writes

 * @dev:	pci device struct

 *

 * Same as pci_cfg_access_lock, but will return 0 if access is

 * already locked, 1 otherwise. This function can be used from

 * atomic contexts.

 */

bool pci_cfg_access_trylock(struct pci_dev *dev)

{

	unsigned long flags;

	int was_blocked;

	bool locked = true;



	raw_spin_lock_irqsave(&pci_lock, flags);

	was_blocked = dev->block_ucfg_access;

	dev->block_ucfg_access = 1;

	if (dev->block_cfg_access)

		locked = false;

	else

		dev->block_cfg_access = 1;

	raw_spin_unlock_irqrestore(&pci_lock, flags);



	/* If we BUG() inside the pci_lock, we're guaranteed to hose

	 * the machine */

	BUG_ON(was_blocked);

	return locked;

}

EXPORT_SYMBOL_GPL(pci_block_user_cfg_access);

EXPORT_SYMBOL_GPL(pci_cfg_access_trylock);



/**

 * pci_unblock_user_cfg_access - Unblock userspace PCI config reads/writes

 * pci_cfg_access_unlock - Unlock PCI config reads/writes

 * @dev:	pci device struct

 *

 * This function allows userspace PCI config accesses to resume.

 * This function allows PCI config accesses to resume.

 */

void pci_unblock_user_cfg_access(struct pci_dev *dev)

void pci_cfg_access_unlock(struct pci_dev *dev)

{

	unsigned long flags;
@@ -438,10 +460,10 @@ void pci_unblock_user_cfg_access(struct pci_dev *dev) 


	/* This indicates a problem in the caller, but we don't need

	 * to kill them, unlike a double-block above. */

	WARN_ON(!dev->block_ucfg_access);

	WARN_ON(!dev->block_cfg_access);



	dev->block_ucfg_access = 0;

	wake_up_all(&pci_ucfg_wait);

	dev->block_cfg_access = 0;

	wake_up_all(&pci_cfg_wait);

	raw_spin_unlock_irqrestore(&pci_lock, flags);

}

EXPORT_SYMBOL_GPL(pci_unblock_user_cfg_access);
 
EXPORT_SYMBOL_GPL(pci_cfg_access_unlock);

drivers/pci/iov.c

+6 −6
Original line number Diff line number Diff line
@@ -348,10 +348,10 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn) 
	}



	iov->ctrl |= PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE;

	pci_block_user_cfg_access(dev);

	pci_cfg_access_lock(dev);

	pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);

	msleep(100);

	pci_unblock_user_cfg_access(dev);

	pci_cfg_access_unlock(dev);



	iov->initial = initial;

	if (nr_virtfn < initial)
@@ -379,10 +379,10 @@ failed: 
		virtfn_remove(dev, j, 0);



	iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);

	pci_block_user_cfg_access(dev);

	pci_cfg_access_lock(dev);

	pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);

	ssleep(1);

	pci_unblock_user_cfg_access(dev);

	pci_cfg_access_unlock(dev);



	if (iov->link != dev->devfn)

		sysfs_remove_link(&dev->dev.kobj, "dep_link");
@@ -405,10 +405,10 @@ static void sriov_disable(struct pci_dev *dev) 
		virtfn_remove(dev, i, 0);



	iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);

	pci_block_user_cfg_access(dev);

	pci_cfg_access_lock(dev);

	pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);

	ssleep(1);

	pci_unblock_user_cfg_access(dev);

	pci_cfg_access_unlock(dev);



	if (iov->link != dev->devfn)

		sysfs_remove_link(&dev->dev.kobj, "dep_link");

drivers/pci/pci.c

+2 −2
Original line number Diff line number Diff line
@@ -2965,7 +2965,7 @@ static int pci_dev_reset(struct pci_dev *dev, int probe) 
	might_sleep();



	if (!probe) {

		pci_block_user_cfg_access(dev);

		pci_cfg_access_lock(dev);

		/* block PM suspend, driver probe, etc. */

		device_lock(&dev->dev);

	}
@@ -2990,7 +2990,7 @@ static int pci_dev_reset(struct pci_dev *dev, int probe) 
done:

	if (!probe) {

		device_unlock(&dev->dev);

		pci_unblock_user_cfg_access(dev);

		pci_cfg_access_unlock(dev);

	}



	return rc;

drivers/scsi/ipr.c

+60 −7
Original line number Diff line number Diff line
@@ -7638,8 +7638,12 @@ static int ipr_reset_restore_cfg_space(struct ipr_cmnd *ipr_cmd) 
 **/

static int ipr_reset_bist_done(struct ipr_cmnd *ipr_cmd)

{

	struct ipr_ioa_cfg *ioa_cfg = ipr_cmd->ioa_cfg;



	ENTER;

	pci_unblock_user_cfg_access(ipr_cmd->ioa_cfg->pdev);

	if (ioa_cfg->cfg_locked)

		pci_cfg_access_unlock(ioa_cfg->pdev);

	ioa_cfg->cfg_locked = 0;

	ipr_cmd->job_step = ipr_reset_restore_cfg_space;

	LEAVE;

	return IPR_RC_JOB_CONTINUE;
@@ -7660,8 +7664,6 @@ static int ipr_reset_start_bist(struct ipr_cmnd *ipr_cmd) 
	int rc = PCIBIOS_SUCCESSFUL;



	ENTER;

	pci_block_user_cfg_access(ioa_cfg->pdev);



	if (ioa_cfg->ipr_chip->bist_method == IPR_MMIO)

		writel(IPR_UPROCI_SIS64_START_BIST,

		       ioa_cfg->regs.set_uproc_interrupt_reg32);
@@ -7673,7 +7675,9 @@ static int ipr_reset_start_bist(struct ipr_cmnd *ipr_cmd) 
		ipr_reset_start_timer(ipr_cmd, IPR_WAIT_FOR_BIST_TIMEOUT);

		rc = IPR_RC_JOB_RETURN;

	} else {

		pci_unblock_user_cfg_access(ipr_cmd->ioa_cfg->pdev);

		if (ioa_cfg->cfg_locked)

			pci_cfg_access_unlock(ipr_cmd->ioa_cfg->pdev);

		ioa_cfg->cfg_locked = 0;

		ipr_cmd->s.ioasa.hdr.ioasc = cpu_to_be32(IPR_IOASC_PCI_ACCESS_ERROR);

		rc = IPR_RC_JOB_CONTINUE;

	}
@@ -7716,7 +7720,6 @@ static int ipr_reset_slot_reset(struct ipr_cmnd *ipr_cmd) 
	struct pci_dev *pdev = ioa_cfg->pdev;



	ENTER;

	pci_block_user_cfg_access(pdev);

	pci_set_pcie_reset_state(pdev, pcie_warm_reset);

	ipr_cmd->job_step = ipr_reset_slot_reset_done;

	ipr_reset_start_timer(ipr_cmd, IPR_PCI_RESET_TIMEOUT);
@@ -7724,6 +7727,56 @@ static int ipr_reset_slot_reset(struct ipr_cmnd *ipr_cmd) 
	return IPR_RC_JOB_RETURN;

}



/**

 * ipr_reset_block_config_access_wait - Wait for permission to block config access

 * @ipr_cmd:	ipr command struct

 *

 * Description: This attempts to block config access to the IOA.

 *

 * Return value:

 * 	IPR_RC_JOB_CONTINUE / IPR_RC_JOB_RETURN

 **/

static int ipr_reset_block_config_access_wait(struct ipr_cmnd *ipr_cmd)

{

	struct ipr_ioa_cfg *ioa_cfg = ipr_cmd->ioa_cfg;

	int rc = IPR_RC_JOB_CONTINUE;



	if (pci_cfg_access_trylock(ioa_cfg->pdev)) {

		ioa_cfg->cfg_locked = 1;

		ipr_cmd->job_step = ioa_cfg->reset;

	} else {

		if (ipr_cmd->u.time_left) {

			rc = IPR_RC_JOB_RETURN;

			ipr_cmd->u.time_left -= IPR_CHECK_FOR_RESET_TIMEOUT;

			ipr_reset_start_timer(ipr_cmd,

					      IPR_CHECK_FOR_RESET_TIMEOUT);

		} else {

			ipr_cmd->job_step = ioa_cfg->reset;

			dev_err(&ioa_cfg->pdev->dev,

				"Timed out waiting to lock config access. Resetting anyway.\n");

		}

	}



	return rc;

}



/**

 * ipr_reset_block_config_access - Block config access to the IOA

 * @ipr_cmd:	ipr command struct

 *

 * Description: This attempts to block config access to the IOA

 *

 * Return value:

 * 	IPR_RC_JOB_CONTINUE

 **/

static int ipr_reset_block_config_access(struct ipr_cmnd *ipr_cmd)

{

	ipr_cmd->ioa_cfg->cfg_locked = 0;

	ipr_cmd->job_step = ipr_reset_block_config_access_wait;

	ipr_cmd->u.time_left = IPR_WAIT_FOR_RESET_TIMEOUT;

	return IPR_RC_JOB_CONTINUE;

}



/**

 * ipr_reset_allowed - Query whether or not IOA can be reset

 * @ioa_cfg:	ioa config struct
@@ -7763,7 +7816,7 @@ static int ipr_reset_wait_to_start_bist(struct ipr_cmnd *ipr_cmd) 
		ipr_cmd->u.time_left -= IPR_CHECK_FOR_RESET_TIMEOUT;

		ipr_reset_start_timer(ipr_cmd, IPR_CHECK_FOR_RESET_TIMEOUT);

	} else {

		ipr_cmd->job_step = ioa_cfg->reset;

		ipr_cmd->job_step = ipr_reset_block_config_access;

		rc = IPR_RC_JOB_CONTINUE;

	}
@@ -7796,7 +7849,7 @@ static int ipr_reset_alert(struct ipr_cmnd *ipr_cmd) 
		writel(IPR_UPROCI_RESET_ALERT, ioa_cfg->regs.set_uproc_interrupt_reg32);

		ipr_cmd->job_step = ipr_reset_wait_to_start_bist;

	} else {

		ipr_cmd->job_step = ioa_cfg->reset;

		ipr_cmd->job_step = ipr_reset_block_config_access;

	}



	ipr_cmd->u.time_left = IPR_WAIT_FOR_RESET_TIMEOUT;

drivers/scsi/ipr.h

+1 −0
Original line number Diff line number Diff line
@@ -1387,6 +1387,7 @@ struct ipr_ioa_cfg { 
	u8 msi_received:1;

	u8 sis64:1;

	u8 dump_timeout:1;

	u8 cfg_locked:1;



	u8 revid;

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