Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 216.228.112.34 as permitted sender) receiver=protection.outlook.com;
 client-ip=216.228.112.34; helo=mail.nvidia.com;
Subject: Re: [PATCH 09/11] PCI: add matching checks for driver_override
 binding
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>
References: <20210615150458.GR1002214@nvidia.com>
 <20210615102049.71a3c125.alex.williamson@redhat.com>
 <20210615204216.GY1002214@nvidia.com>
 <20210615155900.51f09c15.alex.williamson@redhat.com>
 <20210615230017.GZ1002214@nvidia.com>
 <20210615172242.4b2be854.alex.williamson@redhat.com>
 <20210615233257.GB1002214@nvidia.com>
 <20210615182245.54944509.alex.williamson@redhat.com>
 <20210616003417.GH1002214@nvidia.com>
 <cd95b92c-a23b-03a7-1dd3-9554b9d22955@nvidia.com>
 <20210616233317.GR1002214@nvidia.com>
From:   Max Gurtovoy <mgurtovoy@nvidia.com>
Message-ID: <f6ef5c0c-0a85-30ca-5711-3b86d71c141a@nvidia.com>
Date:   Thu, 17 Jun 2021 02:42:46 +0300
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <20210616233317.GR1002214@nvidia.com>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jun 2021 23:42:55.0460
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 1deb4bb2-d99c-455b-5b8c-08d9312076d6
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT017.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR1201MB2553
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


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