linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Don Dutile <ddutile@redhat.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bjorn Helgaas <helgaas@kernel.org>
Cc: "Leon Romanovsky" <leon@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Saeed Mahameed" <saeedm@nvidia.com>,
	"Jason Gunthorpe" <jgg@nvidia.com>,
	"Alexander Duyck" <alexander.duyck@gmail.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	linux-pci@vger.kernel.org, linux-rdma@vger.kernel.org,
	netdev@vger.kernel.org,
	"Alex Williamson" <alex.williamson@redhat.com>,
	"David S . Miller" <davem@davemloft.net>,
	"Krzysztof Wilczyński" <kw@linux.com>
Subject: Re: [PATCH mlx5-next v6 1/4] PCI: Add sysfs callback to allow MSI-X table size change of SR-IOV VFs
Date: Wed, 24 Feb 2021 16:37:40 -0500	[thread overview]
Message-ID: <f88031ee-699f-458f-c8f5-952f2a24e723@redhat.com> (raw)
In-Reply-To: <YDYJpTaxXL4ESwZS@kroah.com>

On 2/24/21 3:09 AM, Greg Kroah-Hartman wrote:
> On Tue, Feb 23, 2021 at 03:07:43PM -0600, Bjorn Helgaas wrote:
>> On Sun, Feb 21, 2021 at 08:59:18AM +0200, Leon Romanovsky wrote:
>>> On Sat, Feb 20, 2021 at 01:06:00PM -0600, Bjorn Helgaas wrote:
>>>> On Fri, Feb 19, 2021 at 09:20:18AM +0100, Greg Kroah-Hartman wrote:
>>>>
>>>>> Ok, can you step back and try to explain what problem you are trying to
>>>>> solve first, before getting bogged down in odd details?  I find it
>>>>> highly unlikely that this is something "unique", but I could be wrong as
>>>>> I do not understand what you are wanting to do here at all.
>>>> We want to add two new sysfs files:
>>>>
>>>>    sriov_vf_total_msix, for PF devices
>>>>    sriov_vf_msix_count, for VF devices associated with the PF
>>>>
>>>> AFAICT it is *acceptable* if they are both present always.  But it
>>>> would be *ideal* if they were only present when a driver that
>>>> implements the ->sriov_get_vf_total_msix() callback is bound to the
>>>> PF.
>>> BTW, we already have all possible combinations: static, static with
>>> folder, with and without "sriov_" prefix, dynamic with and without
>>> folders on VFs.
>>>
>>> I need to know on which version I'll get Acked-by and that version I
>>> will resubmit.
>> I propose that you make static attributes for both files, so
>> "sriov_vf_total_msix" is visible for *every* PF in the system and
>> "sriov_vf_msix_count" is visible for *every* VF in the system.
>>
>> The PF "sriov_vf_total_msix" show function can return zero if there's
>> no PF driver or it doesn't support ->sriov_get_vf_total_msix().
>> (Incidentally, I think the documentation should mention that when it
>> *is* supported, the contents of this file are *constant*, i.e., it
>> does not decrease as vectors are assigned to VFs.)
>>
>> The "sriov_vf_msix_count" set function can ignore writes if there's no
>> PF driver or it doesn't support ->sriov_get_vf_total_msix(), or if a
>> VF driver is bound.
>>
>> Any userspace software must be able to deal with those scenarios
>> anyway, so I don't think the mere presence or absence of the files is
>> a meaningful signal to that software.
> Hopefully, good luck with that!
Management sw is use to dealing with optional sysfs files.
libvirt does that now with the VF files for a PF -- all PF's don't have VFs.
The VF files are only created if a VF ext-cfg-hdr exists.

So, as Bjorn said, mgmt sw related to optionally tuning PCIe devices are designed to check for file existence.

>> If we figure out a way to make the files visible only when the
>> appropriate driver is bound, that might be nice and could always be
>> done later.  But I don't think it's essential.
> That seems reasonable, feel free to cc: me on the next patch series and
> I'll try to review it, which should make more sense to me than this
> email thread :)
>
> thanks,
>
> greg k-h
>


  reply	other threads:[~2021-02-24 21:39 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-09 13:34 [PATCH mlx5-next v6 0/4] Dynamically assign MSI-X vectors count Leon Romanovsky
2021-02-09 13:34 ` [PATCH mlx5-next v6 1/4] PCI: Add sysfs callback to allow MSI-X table size change of SR-IOV VFs Leon Romanovsky
2021-02-15 21:01   ` Bjorn Helgaas
2021-02-16  7:33     ` Leon Romanovsky
2021-02-16 16:12       ` Bjorn Helgaas
2021-02-16 19:58         ` Leon Romanovsky
2021-02-17 18:02           ` Bjorn Helgaas
2021-02-17 19:25             ` Jason Gunthorpe
2021-02-17 20:28               ` Bjorn Helgaas
2021-02-17 23:52                 ` Jason Gunthorpe
2021-02-18 10:15             ` Leon Romanovsky
2021-02-18 22:39               ` Bjorn Helgaas
2021-02-19  7:52                 ` Leon Romanovsky
2021-02-19  8:20                   ` Greg Kroah-Hartman
2021-02-19 16:58                     ` Leon Romanovsky
2021-02-20 19:06                     ` Bjorn Helgaas
2021-02-21  6:59                       ` Leon Romanovsky
2021-02-23 21:07                         ` Bjorn Helgaas
2021-02-24  8:09                           ` Greg Kroah-Hartman
2021-02-24 21:37                             ` Don Dutile [this message]
2021-02-24  9:53                           ` Leon Romanovsky
2021-02-24 15:07                             ` Bjorn Helgaas
2021-02-21 13:00                       ` Greg Kroah-Hartman
2021-02-21 13:55                         ` Leon Romanovsky
2021-02-21 15:01                           ` Greg Kroah-Hartman
2021-02-21 15:30                             ` Leon Romanovsky
2021-02-16 20:37         ` Jason Gunthorpe
2021-02-09 13:34 ` [PATCH mlx5-next v6 2/4] net/mlx5: Add dynamic MSI-X capabilities bits Leon Romanovsky
2021-02-09 13:34 ` [PATCH mlx5-next v6 3/4] net/mlx5: Dynamically assign MSI-X vectors count Leon Romanovsky
2021-02-09 13:34 ` [PATCH mlx5-next v6 4/4] net/mlx5: Allow to the users to configure number of MSI-X vectors Leon Romanovsky
2021-02-09 21:06 ` [PATCH mlx5-next v6 0/4] Dynamically assign MSI-X vectors count Alexander Duyck
2021-02-14  5:24   ` Leon Romanovsky

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=f88031ee-699f-458f-c8f5-952f2a24e723@redhat.com \
    --to=ddutile@redhat.com \
    --cc=alex.williamson@redhat.com \
    --cc=alexander.duyck@gmail.com \
    --cc=bhelgaas@google.com \
    --cc=davem@davemloft.net \
    --cc=gregkh@linuxfoundation.org \
    --cc=helgaas@kernel.org \
    --cc=jgg@nvidia.com \
    --cc=kuba@kernel.org \
    --cc=kw@linux.com \
    --cc=leon@kernel.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=linux-rdma@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=saeedm@nvidia.com \
    --subject='Re: [PATCH mlx5-next v6 1/4] PCI: Add sysfs callback to allow MSI-X table size change of SR-IOV VFs' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).