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Date: Mon, 29 Aug 2011 17:42:16 +0200
From: Jan Kiszka <jan.kiszka@...mens.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
CC: Jesse Barnes <jbarnes@...tuousgeek.org>,
Brian King <brking@...ibm.com>,
"James E.J. Bottomley" <JBottomley@...allels.com>,
"Hans J. Koch" <hjk@...sjkoch.de>,
Greg Kroah-Hartman <gregkh@...e.de>, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
kvm@...r.kernel.org
Subject: Re: Broken pci_block_user_cfg_access interface
On 2011-08-29 17:05, Michael S. Tsirkin wrote:
> So how about something like the following?
> Compile tested only, and I'm not sure I got the
> ipr and iov error handling right.
> Comments?
This still doesn't synchronize two callers of pci_block_user_cfg_access
unless one was reset. We may not have such a scenario yet, but that's
how the old code started as well...
And it makes the interface more convoluted (from 10000 meter, why should
pci_block_user_cfg_access return an error if reset is running?).
>
> ---->
> Subject: [PATCH] pci: fail block usercfg access on reset
>
> Anyone who wants to block usercfg access will
> also want to block reset from userspace.
> On the other hand, reset from userspace
> should block any other access from userspace.
>
> Finally, make it possible to detect reset in
> pregress by returning an error status from
> pci_block_user_cfg_access.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
> drivers/pci/access.c | 45 ++++++++++++++++++++++++++++++++++++----
> drivers/pci/iov.c | 19 ++++++++++++----
> drivers/pci/pci.c | 4 +-
> drivers/scsi/ipr.c | 22 ++++++++++++++++++-
> drivers/uio/uio_pci_generic.c | 7 +++++-
> include/linux/pci.h | 6 ++++-
> 6 files changed, 87 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/pci/access.c b/drivers/pci/access.c
> index fdaa42a..2492365 100644
> --- a/drivers/pci/access.c
> +++ b/drivers/pci/access.c
> @@ -139,7 +139,7 @@ static noinline void pci_wait_ucfg(struct pci_dev *dev)
> raw_spin_unlock_irq(&pci_lock);
> schedule();
> raw_spin_lock_irq(&pci_lock);
> - } while (dev->block_ucfg_access);
> + } while (dev->block_ucfg_access || dev->reset_in_progress);
> __remove_wait_queue(&pci_ucfg_wait, &wait);
> }
>
> @@ -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_ucfg_access || dev->reset_in_progress)) \
> + pci_wait_ucfg(dev); \
> ret = dev->bus->ops->read(dev->bus, dev->devfn, \
> pos, sizeof(type), &data); \
> raw_spin_unlock_irq(&pci_lock); \
> @@ -171,8 +172,9 @@ int pci_user_write_config_##size \
> int ret = -EIO; \
> if (PCI_##size##_BAD) \
> return -EINVAL; \
> - raw_spin_lock_irq(&pci_lock); \
> - if (unlikely(dev->block_ucfg_access)) pci_wait_ucfg(dev); \
> + raw_spin_lock_irq(&pci_lock); \
> + if (unlikely(dev->block_ucfg_access || dev->reset_in_progress)) \
> + pci_wait_ucfg(dev); \
> ret = dev->bus->ops->write(dev->bus, dev->devfn, \
> pos, sizeof(type), val); \
> raw_spin_unlock_irq(&pci_lock); \
> @@ -408,19 +410,24 @@ EXPORT_SYMBOL(pci_vpd_truncate);
> * sleep until access is unblocked again. We don't allow nesting of
> * block/unblock calls.
> */
> -void pci_block_user_cfg_access(struct pci_dev *dev)
> +int pci_block_user_cfg_access(struct pci_dev *dev)
> {
> unsigned long flags;
> int was_blocked;
> + int in_progress;
>
> raw_spin_lock_irqsave(&pci_lock, flags);
> was_blocked = dev->block_ucfg_access;
> dev->block_ucfg_access = 1;
> + in_progress = dev->reset_in_progress;
> raw_spin_unlock_irqrestore(&pci_lock, flags);
>
> + if (in_progress)
> + return -EIO;
> /* If we BUG() inside the pci_lock, we're guaranteed to hose
> * the machine */
> BUG_ON(was_blocked);
> + return 0;
> }
> EXPORT_SYMBOL_GPL(pci_block_user_cfg_access);
>
> @@ -445,3 +452,31 @@ void pci_unblock_user_cfg_access(struct pci_dev *dev)
> raw_spin_unlock_irqrestore(&pci_lock, flags);
> }
> EXPORT_SYMBOL_GPL(pci_unblock_user_cfg_access);
> +
> +void pci_reset_start(struct pci_dev *dev)
> +{
> + int was_started;
> +
> + raw_spin_lock_irq(&pci_lock);
> + if (unlikely(dev->block_ucfg_access || dev->reset_in_progress))
> + pci_wait_ucfg(dev);
> + was_started = dev->reset_in_progress;
> + dev->reset_in_progress = 1;
> + raw_spin_unlock_irq(&pci_lock);
> +
> + /* If we BUG() inside the pci_lock, we're guaranteed to hose
> + * the machine */
> + BUG_ON(was_started);
> +}
> +void pci_reset_end(struct pci_dev *dev)
> +{
> + raw_spin_lock_irq(&pci_lock);
> +
> + /* This indicates a problem in the caller, but we don't need
> + * to kill them, unlike a double-reset above. */
> + WARN_ON(!dev->reset_in_progress);
> +
> + dev->reset_in_progress = 0;
> + wake_up_all(&pci_ucfg_wait);
> + raw_spin_unlock_irq(&pci_lock);
> +}
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 42fae47..464d9b5 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -275,7 +275,7 @@ static void sriov_disable_migration(struct pci_dev *dev)
>
> static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
> {
> - int rc;
> + int rc, rc1;
> int i, j;
> int nres;
> u16 offset, stride, initial;
> @@ -340,7 +340,10 @@ 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);
> + rc = pci_block_user_cfg_access(dev);
> + if (rc)
> + goto err;
> +
> pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
> msleep(100);
> pci_unblock_user_cfg_access(dev);
> @@ -371,11 +374,14 @@ failed:
> virtfn_remove(dev, j, 0);
>
> iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);
> - pci_block_user_cfg_access(dev);
> + rc1 = pci_block_user_cfg_access(dev);
> + if (rc1)
> + goto err;
> pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
> ssleep(1);
> pci_unblock_user_cfg_access(dev);
>
> +err:
> if (iov->link != dev->devfn)
> sysfs_remove_link(&dev->dev.kobj, "dep_link");
>
> @@ -384,7 +390,7 @@ failed:
>
> static void sriov_disable(struct pci_dev *dev)
> {
> - int i;
> + int i, rc;
> struct pci_sriov *iov = dev->sriov;
>
> if (!iov->nr_virtfn)
> @@ -397,11 +403,14 @@ 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);
> + rc = pci_block_user_cfg_access(dev);
> + if (rc)
> + goto err;
> pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
> ssleep(1);
> pci_unblock_user_cfg_access(dev);
>
> +err:
> if (iov->link != dev->devfn)
> sysfs_remove_link(&dev->dev.kobj, "dep_link");
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 0ce6742..815efc2 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -2959,7 +2959,7 @@ static int pci_dev_reset(struct pci_dev *dev, int probe)
> might_sleep();
>
> if (!probe) {
> - pci_block_user_cfg_access(dev);
> + pci_reset_start(dev);
> /* block PM suspend, driver probe, etc. */
> device_lock(&dev->dev);
> }
> @@ -2984,7 +2984,7 @@ 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_reset_end(dev);
> }
>
> return rc;
> diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
> index 8d63630..d322da3 100644
> --- a/drivers/scsi/ipr.c
> +++ b/drivers/scsi/ipr.c
> @@ -7661,7 +7661,9 @@ static int ipr_reset_start_bist(struct ipr_cmnd *ipr_cmd)
> int rc = PCIBIOS_SUCCESSFUL;
>
> ENTER;
> - pci_block_user_cfg_access(ioa_cfg->pdev);
> + rc = pci_block_user_cfg_access(ioa_cfg->pdev);
> + if (rc)
> + goto err;
>
> if (ioa_cfg->ipr_chip->bist_method == IPR_MMIO)
> writel(IPR_UPROCI_SIS64_START_BIST,
> @@ -7681,6 +7683,13 @@ static int ipr_reset_start_bist(struct ipr_cmnd *ipr_cmd)
>
> LEAVE;
> return rc;
> +
> +err:
> +
> + ipr_cmd->s.ioasa.hdr.ioasc = cpu_to_be32(IPR_IOASC_PCI_ACCESS_ERROR);
> + rc = IPR_RC_JOB_CONTINUE;
> + LEAVE;
> + return rc;
> }
>
> /**
> @@ -7715,14 +7724,23 @@ static int ipr_reset_slot_reset(struct ipr_cmnd *ipr_cmd)
> {
> struct ipr_ioa_cfg *ioa_cfg = ipr_cmd->ioa_cfg;
> struct pci_dev *pdev = ioa_cfg->pdev;
> + int rc;
>
> ENTER;
> - pci_block_user_cfg_access(pdev);
> + rc = pci_block_user_cfg_access(pdev);
> + if (rc)
> + goto err;
Looks like the target for this jump is missing.
> +
> 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);
> LEAVE;
> return IPR_RC_JOB_RETURN;
> +
> + ipr_cmd->s.ioasa.hdr.ioasc = cpu_to_be32(IPR_IOASC_PCI_ACCESS_ERROR);
> + rc = IPR_RC_JOB_CONTINUE;
> + LEAVE;
> + return rc;
> }
>
> /**
> diff --git a/drivers/uio/uio_pci_generic.c b/drivers/uio/uio_pci_generic.c
> index fc22e1e..a26d35f 100644
> --- a/drivers/uio/uio_pci_generic.c
> +++ b/drivers/uio/uio_pci_generic.c
> @@ -51,6 +51,7 @@ static irqreturn_t irqhandler(int irq, struct uio_info *info)
> irqreturn_t ret = IRQ_NONE;
> u32 cmd_status_dword;
> u16 origcmd, newcmd, status;
> + int r;
>
> /* We do a single dword read to retrieve both command and status.
> * Document assumptions that make this possible. */
> @@ -58,7 +59,9 @@ static irqreturn_t irqhandler(int irq, struct uio_info *info)
> BUILD_BUG_ON(PCI_COMMAND + 2 != PCI_STATUS);
>
> spin_lock_irq(&gdev->lock);
> - pci_block_user_cfg_access(pdev);
> + r = pci_block_user_cfg_access(pdev);
> + if (r < 0)
> + goto err;
>
> /* Read both command and status registers in a single 32-bit operation.
> * Note: we could cache the value for command and move the status read
> @@ -83,6 +86,8 @@ static irqreturn_t irqhandler(int irq, struct uio_info *info)
> done:
>
> pci_unblock_user_cfg_access(pdev);
> +err:
> +
> spin_unlock_irq(&gdev->lock);
> return ret;
> }
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 8c230cb..ec3b8fe 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -322,6 +322,7 @@ struct pci_dev {
> unsigned int is_hotplug_bridge:1;
> unsigned int __aer_firmware_first_valid:1;
> unsigned int __aer_firmware_first:1;
> + unsigned int reset_in_progress:1;
> pci_dev_flags_t dev_flags;
> atomic_t enable_cnt; /* pci_enable_device has been called */
>
> @@ -1079,9 +1080,12 @@ int ht_create_irq(struct pci_dev *dev, int idx);
> void ht_destroy_irq(unsigned int irq);
> #endif /* CONFIG_HT_IRQ */
>
> -extern void pci_block_user_cfg_access(struct pci_dev *dev);
> +extern int pci_block_user_cfg_access(struct pci_dev *dev);
> extern void pci_unblock_user_cfg_access(struct pci_dev *dev);
>
> +extern void pci_reset_start(struct pci_dev *dev);
> +extern void pci_reset_end(struct pci_dev *dev);
> +
> /*
> * PCI domain support. Sometimes called PCI segment (eg by ACPI),
> * a PCI domain is defined to be a set of PCI busses which share
I still don't get what prevents converting ipr to allow plain mutex
synchronization. My vision is:
- push reset-on-error of ipr into workqueue (or threaded IRQ?)
- require mutex synchronization for common config space access and the
full reset cycle
- only exception: INTx status/masking access
=> use pci_lock + test for reset_in_progress, skip operation if
that is the case
That would allow to drop the whole block_user_cfg infrastructure.
Jan
--
Siemens AG, Corporate Technology, CT T DE IT 1
Corporate Competence Center Embedded Linux
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