Re: [PATCH] PCI: Move test of INTx masking to pci_setup_device
From: Bjorn Helgaas
Date: Fri Jun 16 2017 - 18:55:09 EST
On Fri, May 26, 2017 at 10:02:25PM +0100, Piotr Gregor wrote:
> The test for INTx masking via config space command performed
> in pci_intx_mask_supported() should be performed before PCI device
> can be used. This is to avoid reading/writing of PCI_COMMAND_INTX_DISABLE
> register which may collide with MSI/MSI-X interrupts.
>
> This patch moves test performed in pci_intx_mask_supported() to
>
> static void pci_test_intx_masking(struct pci_dev *dev)
>
> defined in drivers/pci/probe.c.
>
> This function is called from pci_setup_device(). It skips the test
> if the device has been already marked to have broken INTx masking
> feature. Otherwise the test is executed and broken_intx_masking
> field of struct pci_dev is set accordingly. broken_intx_masking
> meaning is: if it is true then the test has been either skipped
> because the device has been already known to have broken INTx
> masking support, or the test's been done and it has detected INTx
> masking support to be broken.
> The test result can be queried at any time later from the pci_dev
> using same interface as before (though whith changed implementation)
>
> static inline bool pci_intx_mask_supported(struct pci_dev *pdev)
> {
> /*
> * INTx masking is supported if device has not been marked
> * to have this feature broken and it has passed
> * pci_test_intx_masking() test.
> */
> return !pdev->broken_intx_masking;
> }
>
> so current users of pci_intx_mask_supported: uio and vfio, keep
> their code unchanged.
>
> Signed-off-by: Piotr Gregor <piotrgregor@xxxxxxxxxxx>
> ---
> drivers/pci/pci.c | 42 +-----------------------------------------
> drivers/pci/probe.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pci.h | 13 +++++++++++--
> 3 files changed, 56 insertions(+), 43 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b01bd5b..7c4e1aa 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3708,46 +3708,6 @@ void pci_intx(struct pci_dev *pdev, int enable)
> }
> EXPORT_SYMBOL_GPL(pci_intx);
>
> -/**
> - * pci_intx_mask_supported - probe for INTx masking support
> - * @dev: the PCI device to operate on
> - *
> - * Check if the device dev support INTx masking via the config space
> - * command word.
> - */
> -bool pci_intx_mask_supported(struct pci_dev *dev)
> -{
> - bool mask_supported = false;
> - u16 orig, new;
> -
> - if (dev->broken_intx_masking)
> - return false;
> -
> - pci_cfg_access_lock(dev);
> -
> - pci_read_config_word(dev, PCI_COMMAND, &orig);
> - pci_write_config_word(dev, PCI_COMMAND,
> - orig ^ PCI_COMMAND_INTX_DISABLE);
> - pci_read_config_word(dev, PCI_COMMAND, &new);
> -
> - /*
> - * There's no way to protect against hardware bugs or detect them
> - * reliably, but as long as we know what the value should be, let's
> - * go ahead and check it.
> - */
> - if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
> - dev_err(&dev->dev, "Command register changed from 0x%x to 0x%x: driver or hardware bug?\n",
> - orig, new);
> - } else if ((new ^ orig) & PCI_COMMAND_INTX_DISABLE) {
> - mask_supported = true;
> - pci_write_config_word(dev, PCI_COMMAND, orig);
> - }
> -
> - pci_cfg_access_unlock(dev);
> - return mask_supported;
> -}
> -EXPORT_SYMBOL_GPL(pci_intx_mask_supported);
> -
> static bool pci_check_and_set_intx_mask(struct pci_dev *dev, bool mask)
> {
> struct pci_bus *bus = dev->bus;
> @@ -3798,7 +3758,7 @@ static bool pci_check_and_set_intx_mask(struct pci_dev *dev, bool mask)
> * @dev: the PCI device to operate on
> *
> * Check if the device dev has its INTx line asserted, mask it and
> - * return true in that case. False is returned if not interrupt was
> + * return true in that case. False is returned if no interrupt was
> * pending.
> */
> bool pci_check_and_mask_intx(struct pci_dev *dev)
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 19c8950..ee6b55c 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1330,6 +1330,48 @@ static void pci_msi_setup_pci_dev(struct pci_dev *dev)
> }
>
> /**
> + * pci_test_intx_masking - probe for INTx masking support
> + * @dev: the PCI device to operate on
> + *
> + * Check if the @dev supports INTx masking via the config space
> + * command word. Executed when PCI device is setup. Result is saved
> + * in broken_intx_masking field of struct pci_dev and can be checked
> + * with pci_intx_mask_supported at any time later, after the PCI device
> + * has been setup (this avoids testing of PCI_COMMAND_INTX_DISABLE
> + * register at runtime).
> + */
> +static void pci_test_intx_masking(struct pci_dev *dev)
> +{
> + u16 orig, toggle, new;
> +
> + /*
> + * If device doesn't support this feature though it could pass the test.
> + */
> + if (dev->broken_intx_masking)
> + return;
I don't think we need this check anymore, because broken_intx_masking
is only set by "FINAL" quirks, which run long after this code.
> +
> + pci_cfg_access_lock(dev);
I don't think we need this locking either. This lock protects against
user-space config access, and the device isn't accessible to user
space yet.
> + /*
> + * Perform the test.
> + */
> + pci_read_config_word(dev, PCI_COMMAND, &orig);
> + toggle = orig ^ PCI_COMMAND_INTX_DISABLE;
> + pci_write_config_word(dev, PCI_COMMAND, toggle);
> + pci_read_config_word(dev, PCI_COMMAND, &new);
> +
> + /*
> + * Restore initial state.
> + */
> + pci_write_config_word(dev, PCI_COMMAND, orig);
> +
> + pci_cfg_access_unlock(dev);
> +
> + if (new != toggle)
> + dev->broken_intx_masking = 1;
> +}
> +
> +/**
> * pci_setup_device - fill in class and map information of a device
> * @dev: the device structure to fill
> *
> @@ -1399,6 +1441,8 @@ int pci_setup_device(struct pci_dev *dev)
> }
> }
>
> + pci_test_intx_masking(dev);
I think it's nicer to read the code if the assignment isn't hidden
away, e.g., something like this:
dev->broken_intx_masking = pci_test_intx_masking(dev);
That's more like what we do for dev->cfg_size and similar things.
I provisionally made these changes and attached the updated patch below.
Let me know if it looks OK.
This is on my pci/enumeration branch, intended for v4.13.
> switch (dev->hdr_type) { /* header type */
> case PCI_HEADER_TYPE_NORMAL: /* standard header */
> if (class == PCI_CLASS_BRIDGE_PCI)
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 33c2b0b..8a307fc 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -366,7 +366,7 @@ struct pci_dev {
> unsigned int is_thunderbolt:1; /* Thunderbolt controller */
> unsigned int __aer_firmware_first_valid:1;
> unsigned int __aer_firmware_first:1;
> - unsigned int broken_intx_masking:1;
> + unsigned int broken_intx_masking:1; /* INTx masking can't be used */
> unsigned int io_window_1k:1; /* Intel P2P bridge 1K I/O windows */
> unsigned int irq_managed:1;
> unsigned int has_secondary_link:1;
> @@ -1003,6 +1003,16 @@ int __must_check pci_reenable_device(struct pci_dev *);
> int __must_check pcim_enable_device(struct pci_dev *pdev);
> void pcim_pin_device(struct pci_dev *pdev);
>
> +static inline bool pci_intx_mask_supported(struct pci_dev *pdev)
> +{
> + /*
> + * INTx masking is supported if device has not been marked
> + * to have this feature broken and it has passed
> + * pci_test_intx_masking() test.
> + */
> + return !pdev->broken_intx_masking;
> +}
> +
> static inline int pci_is_enabled(struct pci_dev *pdev)
> {
> return (atomic_read(&pdev->enable_cnt) > 0);
> @@ -1026,7 +1036,6 @@ int __must_check pci_set_mwi(struct pci_dev *dev);
> int pci_try_set_mwi(struct pci_dev *dev);
> void pci_clear_mwi(struct pci_dev *dev);
> void pci_intx(struct pci_dev *dev, int enable);
> -bool pci_intx_mask_supported(struct pci_dev *dev);
> bool pci_check_and_mask_intx(struct pci_dev *dev);
> bool pci_check_and_unmask_intx(struct pci_dev *dev);
> int pci_wait_for_pending(struct pci_dev *dev, int pos, u16 mask);
commit 73ab6bc006ba966e233785577a1742c6cace9c8a
Author: Piotr Gregor <piotrgregor@xxxxxxxxxxx>
Date: Fri May 26 22:02:25 2017 +0100
PCI: Test INTx masking during enumeration, not at run-time
The test for INTx masking via PCI_COMMAND_INTX_DISABLE performed in
pci_intx_mask_supported() should be done before the device can be used.
This is to avoid writing PCI_COMMAND while the driver owns the device, in
case that has any effect on MSI/MSI-X interrupts.
Move the content of pci_intx_mask_supported() to pci_intx_mask_broken() and
call it from pci_setup_device().
The test result can be queried at any time later using the same
pci_intx_mask_supported() interface as before (though with changed
implementation), so callers (uio, vfio) should be unaffected.
Signed-off-by: Piotr Gregor <piotrgregor@xxxxxxxxxxx>
[bhelgaas: changelog, remove quirk check, remove locking, move
dev->broken_intx_masking assignment to caller]
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b01bd5bba8e6..7c4e1aa67c67 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3708,46 +3708,6 @@ void pci_intx(struct pci_dev *pdev, int enable)
}
EXPORT_SYMBOL_GPL(pci_intx);
-/**
- * pci_intx_mask_supported - probe for INTx masking support
- * @dev: the PCI device to operate on
- *
- * Check if the device dev support INTx masking via the config space
- * command word.
- */
-bool pci_intx_mask_supported(struct pci_dev *dev)
-{
- bool mask_supported = false;
- u16 orig, new;
-
- if (dev->broken_intx_masking)
- return false;
-
- pci_cfg_access_lock(dev);
-
- pci_read_config_word(dev, PCI_COMMAND, &orig);
- pci_write_config_word(dev, PCI_COMMAND,
- orig ^ PCI_COMMAND_INTX_DISABLE);
- pci_read_config_word(dev, PCI_COMMAND, &new);
-
- /*
- * There's no way to protect against hardware bugs or detect them
- * reliably, but as long as we know what the value should be, let's
- * go ahead and check it.
- */
- if ((new ^ orig) & ~PCI_COMMAND_INTX_DISABLE) {
- dev_err(&dev->dev, "Command register changed from 0x%x to 0x%x: driver or hardware bug?\n",
- orig, new);
- } else if ((new ^ orig) & PCI_COMMAND_INTX_DISABLE) {
- mask_supported = true;
- pci_write_config_word(dev, PCI_COMMAND, orig);
- }
-
- pci_cfg_access_unlock(dev);
- return mask_supported;
-}
-EXPORT_SYMBOL_GPL(pci_intx_mask_supported);
-
static bool pci_check_and_set_intx_mask(struct pci_dev *dev, bool mask)
{
struct pci_bus *bus = dev->bus;
@@ -3798,7 +3758,7 @@ static bool pci_check_and_set_intx_mask(struct pci_dev *dev, bool mask)
* @dev: the PCI device to operate on
*
* Check if the device dev has its INTx line asserted, mask it and
- * return true in that case. False is returned if not interrupt was
+ * return true in that case. False is returned if no interrupt was
* pending.
*/
bool pci_check_and_mask_intx(struct pci_dev *dev)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 19c8950c6c38..28c57b31261c 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1329,6 +1329,34 @@ static void pci_msi_setup_pci_dev(struct pci_dev *dev)
pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_ENABLE, 0);
}
+/**
+ * pci_intx_mask_broken - test PCI_COMMAND_INTX_DISABLE writability
+ * @dev: PCI device
+ *
+ * Test whether PCI_COMMAND_INTX_DISABLE is writable for @dev. Check this
+ * at enumeration-time to avoid modifying PCI_COMMAND at run-time.
+ */
+static int pci_intx_mask_broken(struct pci_dev *dev)
+{
+ u16 orig, toggle, new;
+
+ pci_read_config_word(dev, PCI_COMMAND, &orig);
+ toggle = orig ^ PCI_COMMAND_INTX_DISABLE;
+ pci_write_config_word(dev, PCI_COMMAND, toggle);
+ pci_read_config_word(dev, PCI_COMMAND, &new);
+
+ pci_write_config_word(dev, PCI_COMMAND, orig);
+
+ /*
+ * PCI_COMMAND_INTX_DISABLE was reserved and read-only prior to PCI
+ * r2.3, so strictly speaking, a device is not *broken* if it's not
+ * writable.
+ */
+ if (new == toggle)
+ return 1;
+ return 0;
+}
+
/**
* pci_setup_device - fill in class and map information of a device
* @dev: the device structure to fill
@@ -1399,6 +1427,8 @@ int pci_setup_device(struct pci_dev *dev)
}
}
+ dev->broken_intx_masking = pci_intx_mask_broken(dev);
+
switch (dev->hdr_type) { /* header type */
case PCI_HEADER_TYPE_NORMAL: /* standard header */
if (class == PCI_CLASS_BRIDGE_PCI)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 33c2b0b77429..4f0613d5d2d9 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -366,7 +366,7 @@ struct pci_dev {
unsigned int is_thunderbolt:1; /* Thunderbolt controller */
unsigned int __aer_firmware_first_valid:1;
unsigned int __aer_firmware_first:1;
- unsigned int broken_intx_masking:1;
+ unsigned int broken_intx_masking:1; /* INTx masking can't be used */
unsigned int io_window_1k:1; /* Intel P2P bridge 1K I/O windows */
unsigned int irq_managed:1;
unsigned int has_secondary_link:1;
@@ -1003,6 +1003,15 @@ int __must_check pci_reenable_device(struct pci_dev *);
int __must_check pcim_enable_device(struct pci_dev *pdev);
void pcim_pin_device(struct pci_dev *pdev);
+static inline bool pci_intx_mask_supported(struct pci_dev *pdev)
+{
+ /*
+ * INTx masking is supported if PCI_COMMAND_INTX_DISABLE is
+ * writable and no quirk has marked the feature broken.
+ */
+ return !pdev->broken_intx_masking;
+}
+
static inline int pci_is_enabled(struct pci_dev *pdev)
{
return (atomic_read(&pdev->enable_cnt) > 0);
@@ -1026,7 +1035,6 @@ int __must_check pci_set_mwi(struct pci_dev *dev);
int pci_try_set_mwi(struct pci_dev *dev);
void pci_clear_mwi(struct pci_dev *dev);
void pci_intx(struct pci_dev *dev, int enable);
-bool pci_intx_mask_supported(struct pci_dev *dev);
bool pci_check_and_mask_intx(struct pci_dev *dev);
bool pci_check_and_unmask_intx(struct pci_dev *dev);
int pci_wait_for_pending(struct pci_dev *dev, int pos, u16 mask);