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From: Max Gurtovoy <mgurtovoy@nvidia.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>, <cohuck@redhat.com>,
	<kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<aviadye@nvidia.com>, <oren@nvidia.com>, <shahafs@nvidia.com>,
	<parav@nvidia.com>, <artemp@nvidia.com>, <kwankhede@nvidia.com>,
	<ACurrid@nvidia.com>, <cjia@nvidia.com>, <yishaih@nvidia.com>,
	<kevin.tian@intel.com>, <hch@infradead.org>,
	<targupta@nvidia.com>, <shameerali.kolothum.thodi@huawei.com>,
	<liulongfang@huawei.com>, <yan.y.zhao@intel.com>
Subject: Re: [PATCH 09/11] PCI: add matching checks for driver_override binding
Date: Thu, 17 Jun 2021 02:42:46 +0300	[thread overview]
Message-ID: <f6ef5c0c-0a85-30ca-5711-3b86d71c141a@nvidia.com> (raw)
In-Reply-To: <20210616233317.GR1002214@nvidia.com>


On 6/17/2021 2:33 AM, Jason Gunthorpe wrote:
> On Thu, Jun 17, 2021 at 02:28:36AM +0300, Max Gurtovoy wrote:
>> On 6/16/2021 3:34 AM, Jason Gunthorpe wrote:
>>> On Tue, Jun 15, 2021 at 06:22:45PM -0600, Alex Williamson wrote:
>>>> On Tue, 15 Jun 2021 20:32:57 -0300
>>>> Jason Gunthorpe <jgg@nvidia.com> wrote:
>>>>
>>>>> On Tue, Jun 15, 2021 at 05:22:42PM -0600, Alex Williamson wrote:
>>>>>
>>>>>>>> b) alone is a functional, runtime difference.
>>>>>>> I would state b) differently:
>>>>>>>
>>>>>>> b) Ignore the driver-override-only match entries in the ID table.
>>>>>> No, pci_match_device() returns NULL if a match is found that is marked
>>>>>> driver-override-only and a driver_override is not specified.  That's
>>>>>> the same as no match at all.  We don't then go on to search past that
>>>>>> match in the table, we fail to bind the driver.  That's effectively an
>>>>>> anti-match when there's no driver_override on the device.
>>>>> anti-match isn't the intention. The deployment will have match tables
>>>>> where all entires are either flags=0 or are driver-override-only.
>>>> I'd expect pci-pf-stub to have one of each, an any-id with
>>>> override-only flag and the one device ID currently in the table with
>>>> no flag.
>>> Oh Hum. Actually I think this shows the anti-match behavior is
>>> actually a bug.. :(
>>>
>>> For something like pci_pf_stub_whitelist, if we add a
>>> driver_override-only using the PCI any id then it effectively disables
>>> new_id completely because the match search will alway find the
>>> driver_override match first and stop searching. There is no chance to
>>> see things new_id adds.
>> Actually the dynamic table is the first table the driver search. So new_id
>> works exactly the same AFAIU.
> Oh, even better, so it isn't really an issue
>
>> But you're right for static mixed table (I assumed that this will never
>> happen I guess).
> Me too, we could organize the driver-overrides to be last

Yes we could, but in 2 years from now I'll forget this rule :)

And others may not be aware of it.

>   
>> -       found_id = pci_match_id(drv->id_table, dev);
>> -       if (found_id) {
>> +       ids = drv->id_table;
>> +       while ((found_id = pci_match_id(ids, dev))) {
> Yeah, keep searching makes logical sense to me
>
>> diff --git a/drivers/pci/pci-pf-stub.c b/drivers/pci/pci-pf-stub.c
>> index 45855a5e9fca..49544ba9a7af 100644
>> +++ b/drivers/pci/pci-pf-stub.c
>> @@ -19,6 +19,7 @@
>>    */
>>   static const struct pci_device_id pci_pf_stub_whitelist[] = {
>>          { PCI_VDEVICE(AMAZON, 0x0053) },
>> +       { PCI_DEVICE_FLAGS(PCI_ANY_ID, PCI_ANY_ID,
>> PCI_ID_F_STUB_DRIVER_OVERRIDE) }, /* match all by default (override) */
>>          /* required last entry */
>>          { 0 }
> And we don't really want this change any more right? No reason to put
> pci_stub in the module.alias file?

I actually did it in the patches I attached earlier.

It will look like:

stub_pci:v*d*sv*sd*bc*sc*i*

pci:v00001D0Fd00000053sv*sd*bc*sc*i*

I think it's good practice to avoid matching automatically and auto 
loading any_id_override and vfio_override drivers in general.

Do you see a reason not adding this alias for stub drivers but adding it 
to vfio_pci drivers ?

>
> Thanks,
> Jason

  reply	other threads:[~2021-06-16 23:42 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-03 16:07 [RFC PATCH v4 00/11] Introduce vfio-pci-core subsystem Max Gurtovoy
2021-06-03 16:07 ` [PATCH 01/11] vfio-pci: rename vfio_pci.c to vfio_pci_core.c Max Gurtovoy
2021-06-03 16:08 ` [PATCH 02/11] vfio-pci: rename vfio_pci_private.h to vfio_pci_core.h Max Gurtovoy
2021-06-03 16:08 ` [PATCH 03/11] vfio-pci: rename vfio_pci_device to vfio_pci_core_device Max Gurtovoy
2021-06-03 16:08 ` [PATCH 04/11] vfio-pci: rename ops functions to fit core namings Max Gurtovoy
2021-06-03 16:08 ` [PATCH 05/11] vfio-pci: include vfio header in vfio_pci_core.h Max Gurtovoy
2021-06-03 16:08 ` [PATCH 06/11] vfio-pci: introduce vfio_pci.c Max Gurtovoy
2021-06-03 16:08 ` [PATCH 07/11] vfio-pci: move igd initialization to vfio_pci.c Max Gurtovoy
2021-06-03 16:08 ` [PATCH 08/11] PCI: add flags field to pci_device_id structure Max Gurtovoy
2021-06-03 16:08 ` [PATCH 09/11] PCI: add matching checks for driver_override binding Max Gurtovoy
2021-06-08 21:26   ` Alex Williamson
2021-06-08 22:45     ` Jason Gunthorpe
2021-06-09  1:27       ` Alex Williamson
2021-06-09  9:26         ` Max Gurtovoy
2021-06-13  8:19         ` Max Gurtovoy
2021-06-14  5:40           ` Christoph Hellwig
2021-06-14  8:18             ` Max Gurtovoy
2021-06-14 15:27               ` Christoph Hellwig
2021-06-14 16:01                 ` Jason Gunthorpe
2021-06-14 16:15                   ` Christoph Hellwig
2021-06-14 16:33                     ` Jason Gunthorpe
2021-06-14 18:42           ` Alex Williamson
2021-06-14 23:12             ` Max Gurtovoy
2021-06-15 15:00               ` Alex Williamson
2021-06-15 15:04                 ` Jason Gunthorpe
2021-06-15 16:20                   ` Alex Williamson
2021-06-15 20:42                     ` Jason Gunthorpe
2021-06-15 21:59                       ` Alex Williamson
2021-06-15 23:00                         ` Jason Gunthorpe
2021-06-15 23:22                           ` Alex Williamson
2021-06-15 23:32                             ` Jason Gunthorpe
2021-06-16  0:22                               ` Alex Williamson
2021-06-16  0:34                                 ` Jason Gunthorpe
2021-06-16 23:28                                   ` Max Gurtovoy
2021-06-16 23:33                                     ` Jason Gunthorpe
2021-06-16 23:42                                       ` Max Gurtovoy [this message]
2021-06-16 23:44                                         ` Jason Gunthorpe
2021-06-16 23:51                                           ` Max Gurtovoy
2021-06-16 23:56                                             ` Jason Gunthorpe
2021-06-20 14:46                                               ` Max Gurtovoy
2021-06-03 16:08 ` [PATCH 10/11] vfio-pci: introduce vfio_pci_core subsystem driver Max Gurtovoy
2021-06-08 21:26   ` Alex Williamson
2021-06-09  9:29     ` Max Gurtovoy
2021-06-03 16:08 ` [PATCH 11/11] mlx5-vfio-pci: add new vfio_pci driver for mlx5 devices Max Gurtovoy
2021-07-30  7:53 ` [RFC PATCH v4 00/11] Introduce vfio-pci-core subsystem Shameerali Kolothum Thodi
2021-07-30 11:55   ` Jason Gunthorpe

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