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SubjectRe: [PATCH v6 10/30] PCI: Introduce pci_host_bridge_list to manage host bridges
On 2015/3/12 10:55, Bjorn Helgaas wrote:
> On Mon, Mar 09, 2015 at 10:34:07AM +0800, Yijing Wang wrote:
>> Introduce pci_host_bridge_list to manage pci host
>> bridges in system, so we could detect whether
>> the host in domain:bus is alreay registered.
>> Then we could remove bus alreay exist test in
>> __pci_create_root_bus().
>
> It's a nice idea to move this test into the core. While you're at it, why
> don't you check for any overlap with the bus ranges of existing host
> bridges? For example, if we're trying to create a new host bridge to
> [bus 40-7f], it should conflict with existing bridges to [bus 00-7f]
> as well as to [bus 40-ff]. I think your current patch will detect the
> latter conflict but not the former.

Now pci host bridge may only know its start bus number, like acpi _BBN provided,
but does not limit the end bus number, Eg. two pci roots report _BBN 0x0 and 0x80,
so we have two bus number resource (0, 0xff) and (0x80, 0xff), if we check it strictly,
some pci scan would fail which currently scan success.

>
>> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
>> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>> ---
>> drivers/pci/host-bridge.c | 24 +++++++++++++++++++++++-
>> drivers/pci/probe.c | 8 +-------
>> include/linux/pci.h | 1 +
>> 3 files changed, 25 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c
>> index 3bd45e7..0bb08ef 100644
>> --- a/drivers/pci/host-bridge.c
>> +++ b/drivers/pci/host-bridge.c
>> @@ -8,6 +8,9 @@
>>
>> #include "pci.h"
>>
>> +static LIST_HEAD(pci_host_bridge_list);
>> +static DEFINE_MUTEX(phb_mutex);
>
> We don't use the "phb" abbreviation in the PCI core.

OK

>
>> +
>> static void pci_release_host_bridge_dev(struct device *dev)
>> {
>> struct pci_host_bridge *bridge = to_pci_host_bridge(dev);
>> @@ -25,7 +28,7 @@ struct pci_host_bridge *pci_create_host_bridge(
>> int error;
>> int bus = PCI_BUSNUM(db);
>> int domain = PCI_DOMAIN(db);
>> - struct pci_host_bridge *host;
>> + struct pci_host_bridge *host, *temp;
>> struct resource_entry *window, *n;
>>
>> host = kzalloc(sizeof(*host), GFP_KERNEL);
>> @@ -40,6 +43,18 @@ struct pci_host_bridge *pci_create_host_bridge(
>> */
>> pci_host_assign_domain_nr(host);
>>
>> + mutex_lock(&phb_mutex);
>> + list_for_each_entry(temp, &pci_host_bridge_list, list)
>> + if (temp->domain == host->domain
>> + && temp->busnum == host->busnum) {
>> + dev_dbg(&host->dev, "pci host bridge pci%04x:%02x exist\n",
>> + host->domain, host->busnum);
>
> &host->dev hasn't been initialized yet! And the text of the original
> message was better.

Oh, my mistake, good catch.

>
>> + mutex_unlock(&phb_mutex);
>> + kfree(host);
>> + return NULL;
>> + }
>> + mutex_unlock(&phb_mutex);
>
> This is racy. Two CPUs adding a bridge to [bus 00-7f] at about the same
> time can both succeed.
>

Hmm, I need to unlock after I add the new host bridge to the gloal host bridge list, thanks.

> And it needs curly braces around the list_for_each_entry() body.

OK

>
>> +
>> host->dev.parent = parent;
>> INIT_LIST_HEAD(&host->windows);
>> host->dev.release = pci_release_host_bridge_dev;
>> @@ -55,11 +70,18 @@ struct pci_host_bridge *pci_create_host_bridge(
>> resource_list_for_each_entry_safe(window, n, resources)
>> list_move_tail(&window->node, &host->windows);
>>
>> + mutex_lock(&phb_mutex);
>> + list_add_tail(&host->list, &pci_host_bridge_list);
>> + mutex_unlock(&phb_mutex);
>> return host;
>> }
>>
>> void pci_free_host_bridge(struct pci_host_bridge *host)
>> {
>> + mutex_lock(&phb_mutex);
>> + list_del(&host->list);
>> + mutex_unlock(&phb_mutex);
>> +
>> device_unregister(&host->dev);
>> }
>>
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index 27ec612..7238fa3 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -1870,7 +1870,7 @@ static struct pci_bus *__pci_create_root_bus(
>> void *sysdata)
>> {
>> int error;
>> - struct pci_bus *b, *b2;
>> + struct pci_bus *b;
>> struct resource_entry *window;
>> struct device *parent;
>> struct resource *res;
>> @@ -1887,12 +1887,6 @@ static struct pci_bus *__pci_create_root_bus(
>> b->ops = ops;
>> b->number = b->busn_res.start = bridge->busnum;
>> pci_bus_assign_domain_nr(b, parent);
>> - b2 = pci_find_bus(pci_domain_nr(b), b->number);
>> - if (b2) {
>> - /* If we already got to this bus through a different bridge, ignore it */
>> - dev_dbg(&b2->dev, "bus already known\n");
>> - goto err_out;
>> - }
>>
>> bridge->bus = b;
>> b->bridge = get_device(&bridge->dev);
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 463eaa3..b621f5b 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -406,6 +406,7 @@ struct pci_host_bridge {
>> struct device dev;
>> struct pci_bus *bus; /* root bus */
>> struct list_head windows; /* resource_entry */
>> + struct list_head list;
>> void (*release_fn)(struct pci_host_bridge *);
>> void *release_data;
>> };
>> --
>> 1.7.1
>>
>
> .
>


--
Thanks!
Yijing



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