Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751784AbaDAScP (ORCPT ); Tue, 1 Apr 2014 14:32:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12361 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751753AbaDAScM (ORCPT ); Tue, 1 Apr 2014 14:32:12 -0400 From: Bandan Das To: Alex Williamson Cc: Bjorn Helgaas , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PCI: rework new_id interface for known vendor/device values References: <1396371204.476.156.camel@ul30vt.home> Date: Tue, 01 Apr 2014 14:32:09 -0400 In-Reply-To: <1396371204.476.156.camel@ul30vt.home> (Alex Williamson's message of "Tue, 01 Apr 2014 10:53:24 -0600") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alex Williamson writes: > On Mon, 2014-03-31 at 00:28 -0400, Bandan Das wrote: >> While using the new_id interface, the user can unintentionally feed >> incorrect values if the driver static table has a matching entry. >> This is possible since only the device and vendor fields are >> mandatory and the rest are optional. As a result, store_new_id >> will fill in default values that are then passed on to the driver >> and can have unintended consequences. >> >> As an example, consider the ixgbe driver and the 82599EB network card : >> echo "8086 10fb" > /sys/bus/pci/drivers/ixgbe/new_id >> >> This will pass a driver_data value of 0 to the driver whereas >> the index 0 in ixgbe actually points to a different set of card >> operations. >> >> This change automatically selects the matching static entry if there >> is one for the newly created dynid. However, if the user intentionally >> wants a different set of values, she must provide all the 7 fields >> and the static entry will be ignored. >> >> In most cases, this use case seems unnecessary, however, this >> is a common libvirt/KVM/device assignment scenario where the >> user might want to bind a device back to the host driver. >> >> Signed-off-by: Bandan Das >> --- >> drivers/pci/pci-driver.c | 42 ++++++++++++++++++++++++++++++++++++++---- >> 1 file changed, 38 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c >> index 25f0bc6..187e572 100644 >> --- a/drivers/pci/pci-driver.c >> +++ b/drivers/pci/pci-driver.c >> @@ -90,6 +90,24 @@ static void pci_free_dynids(struct pci_driver *drv) >> spin_unlock(&drv->dynids.lock); >> } >> >> +static const struct >> +pci_device_id *match_id_table_entry(struct device_driver *driver, >> + __u32 vendor, __u32 device) >> +{ >> + struct pci_driver *pdrv = to_pci_driver(driver); >> + const struct pci_device_id *ids = pdrv->id_table; >> + >> + if (ids) { >> + while (ids->vendor || ids->subvendor || ids->class_mask) { >> + if ((ids->vendor == vendor) && (ids->device == device)) >> + return ids; >> + ids++; >> + } >> + } >> + >> + return NULL; >> +} >> + >> /** >> * store_new_id - sysfs frontend to pci_add_dynid() >> * @driver: target device driver >> @@ -102,7 +120,8 @@ static ssize_t >> store_new_id(struct device_driver *driver, const char *buf, size_t count) >> { >> struct pci_driver *pdrv = to_pci_driver(driver); >> - const struct pci_device_id *ids = pdrv->id_table; >> + const struct pci_device_id *ids = pdrv->id_table, >> + *tids = NULL; >> __u32 vendor, device, subvendor=PCI_ANY_ID, >> subdevice=PCI_ANY_ID, class=0, class_mask=0; >> unsigned long driver_data=0; >> @@ -115,9 +134,24 @@ store_new_id(struct device_driver *driver, const char *buf, size_t count) >> if (fields < 2) >> return -EINVAL; >> >> - /* Only accept driver_data values that match an existing id_table >> - entry */ >> - if (ids) { >> + tids = match_id_table_entry(driver, vendor, device); >> + > > Would it make more sense to construct a pci_dev, ex: > > if (fields != 7) { > struct pci_dev dev = { .subvendor = PCI_ANY_ID, .subdevice = PCI_ANY_ID }; > > dev.vendor = vendor; > dev.device = device; > if (fields > 2) > dev.subvendor = subvendor; > if (fields > 3) > dev.subdevice = subdevice; > ... > > if (pci_match_id(drv->id_table, &dev)) > return -EEXIST; > } I initially went ahead this way, but the compilation warns about frame size being larger, possibly because of a kernel config option that's set in my config drivers/pci/pci-driver.c:193:1: warning: the frame size of 2264 bytes is larger than 2048 bytes [-Wframe-larger-than=] Do you know if it is safe to ignore this ? This seems to be coming up if I add the struct pdev. > >> + if (tids && (fields != 7)) { >> + >> + subvendor = tids->subvendor; >> + subdevice = tids->subdevice; >> + class = tids->class; >> + class_mask = tids->class_mask; >> + driver_data = tids->driver_data; > > This doesn't look right. First, we're potentially overwriting user > stored data for fields >2 but <7. Second, we only matched on vendor & > device and could be filling the rest with data that isn't the best match > (and is guaranteed to just be a duplicate of a static table ID). > >> + >> + pr_warn("pci: Using driver (%s) static DeviceID table entry for vendor 0x%04x and device 0x%04x", >> + driver->name, vendor, device); > > I think we should be error'ing rather than inventing a duplicate ID to > insert. How would a user ever know how to use remove_id to clean out > this new_id? Thanks, Ok, makes sense to just error out. Good point about remove_id, didn't think about that. Thanks, Bandan > Alex > >> + >> + } else if (ids) { >> + >> + /* Only accept driver_data values that match an existing >> + id_table entry */ >> + >> retval = -EINVAL; >> while (ids->vendor || ids->subvendor || ids->class_mask) { >> if (driver_data == ids->driver_data) { -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/