Hi John:
Thanks for the reviewing, I will fix it in next version.
Ding
On 2017/6/8 1:55, John Garry wrote:
> On 07/06/2017 10:16, Ding Tianhong wrote:
>
> Hi Ding,
>
> A few general style comments:
>
>> The PCIe Device Control Register use the bit 4 to indicate that
>> whether the device is permitted to enable relaxed ordering or not.
>> But relaxed ordering is not safe for some platform which could only
>> use strong write ordering, so devices are allowed (but not required)
>> to enable relaxed ordering bit by default.
>>
>> If a PCIe device didn't enable the relaxed ordering attribute default,
>> we should not do anything in the PCIe configuration, otherwise we
>> should check if any of the devices above us do not support relaxed
>> ordering by the PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag, then base on
>> the result if we get a return that indicate that the relaxed ordering
>> is not supported we should update our device to disable relaxed ordering
>> in configuration space. If the device above us doesn't exist or isn't
>> the PCIe device, we shouldn't do anything and skip updating relaxed ordering
>> because we are probably running in a guest.
>
> A guest machine/environment
>
>>
>> Signed-off-by: Ding Tianhong <dingtianhong@xxxxxxxxxx>
>> ---
>> drivers/pci/pci.c | 29 +++++++++++++++++++++++++++++
>> drivers/pci/probe.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>> include/linux/pci.h | 2 ++
>> 3 files changed, 74 insertions(+)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index b01bd5b..3d42b38 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -4878,6 +4878,35 @@ int pcie_set_mps(struct pci_dev *dev, int mps)
>> EXPORT_SYMBOL(pcie_set_mps);
>>
>> /**
>> + * pcie_clear_relaxed_ordering - clear PCI Express relexed ordering bit
>> + * @dev: PCI device to query
>> + *
>> + * If possible clear relaxed ordering
>> + */
>> +int pcie_clear_relaxed_ordering(struct pci_dev *dev)
>> +{
>> + return pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
>> + PCI_EXP_DEVCTL_RELAX_EN);
>> +}
>> +EXPORT_SYMBOL(pcie_clear_relaxed_ordering);
>> +
>> +/**
>> + * pcie_get_relaxed_ordering - check PCI Express relexed ordering bit
>
> s/relexed/relaxed/
>
> Check what on relaxed ordering bit?
>
> And the function name is inconsistent with this discription.
>
>> + * @dev: PCI device to query
>> + *
>> + * Returns true if relaxed ordering is been set
>
> If you want to return true/false, then use !!, below in the function
>
>> + */
>> +int pcie_get_relaxed_ordering(struct pci_dev *dev)
>> +{
>> + u16 v;
>> +
>> + pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &v);
>> +
>> + return (v & PCI_EXP_DEVCTL_RELAX_EN) >> 4;
>> +}
>> +EXPORT_SYMBOL(pcie_get_relaxed_ordering);
>> +
>> +/**
>> * pcie_get_minimum_link - determine minimum link settings of a PCI device
>> * @dev: PCI device to query
>> * @speed: storage for minimum speed
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index 19c8950..0c94c80 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -1701,6 +1701,48 @@ static void pci_configure_extended_tags(struct pci_dev *dev)
>> PCI_EXP_DEVCTL_EXT_TAG);
>> }
>>
>> +/**
>> + * pci_dev_disable_relaxed_ordering - check if the PCI device
>> + * should disable the relaxed ordering attribute.
>
> I think that we need a more accurate description. I know some people think a function which just "checks" is vague.
>
>> + * @dev: PCI device
>> + *
>> + * Return true if any of the PCI devices above us do not support
>> + * relaxed ordering.
>> + */
>> +static int pci_dev_disable_relaxed_ordering(struct pci_dev *dev)
>
> The function name implies an action - disabling - but this function does nothing except return a value
>
>> +{
>> + int ro_disabled = 0;
>> +
>> + while(dev) {
>
> Did you run checkpatch?
>
>> + if (dev->dev_flags & PCI_DEV_FLAGS_NO_RELAXED_ORDERING) {
>> + ro_disabled = 1;
>
> just return true, and return false at the bottom, so you can do away with ro_disabled (which is not a bool)
>
>> + break;
>> + }
>> + dev = dev->bus->self;
>> + }
>> +
>> + return ro_disabled;
>> +}
>> +
>> +static void pci_configure_relaxed_ordering(struct pci_dev *dev)
>> +{
>> + struct pci_dev *bridge = pci_upstream_bridge(dev);
>> + int origin_ero;
>
> You don't need this variable
>
>> +
>> + if (!pci_is_pcie(dev) || !bridge || !pci_is_pcie(bridge))
>> + return;
>> +
>> + origin_ero = pcie_get_relaxed_ordering(dev);
>> + /* If the releaxed ordering enable bit is not set, do nothing. */
>> + if (!origin_ero)
>> + return;
>> +
>> + if (pci_dev_disable_relaxed_ordering(dev)) {
>> + pcie_clear_relaxed_ordering(dev);
>> + dev_info(&dev->dev, "Disable Relaxed Ordering\n");
>> + }
>> +}
>> +
>> static void pci_configure_device(struct pci_dev *dev)
>> {
>> struct hotplug_params hpp;
>> @@ -1708,6 +1750,7 @@ static void pci_configure_device(struct pci_dev *dev)
>>
>> pci_configure_mps(dev);
>> pci_configure_extended_tags(dev);
>> + pci_configure_relaxed_ordering(dev);
>>
>> memset(&hpp, 0, sizeof(hpp));
>> ret = pci_get_hp_params(dev, &hpp);
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index e1e8428..299d2f3 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -1105,6 +1105,8 @@ int __pci_enable_wake(struct pci_dev *dev, pci_power_t state,
>> void pci_pme_wakeup_bus(struct pci_bus *bus);
>> void pci_d3cold_enable(struct pci_dev *dev);
>> void pci_d3cold_disable(struct pci_dev *dev);
>> +int pcie_clear_relaxed_ordering(struct pci_dev *dev);
>> +int pcie_get_relaxed_ordering(struct pci_dev *dev);
>>
>> static inline int pci_enable_wake(struct pci_dev *dev, pci_power_t state,
>> bool enable)
>>
>
>
>
> .
>
