From: "Hyong Youb Kim (hyonkim)" <hyonkim@cisco.com>
To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>,
Nithin Kumar Dabilpuram <ndabilpuram@marvell.com>,
David Marchand <david.marchand@redhat.com>,
Thomas Monjalon <thomas@monjalon.net>,
Ferruh Yigit <ferruh.yigit@intel.com>,
Bruce Richardson <bruce.richardson@intel.com>
Cc: "John Daley (johndale)" <johndale@cisco.com>,
Shahed Shaikh <shshaikh@marvell.com>,
"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [RFC PATCH v3 2/3] eal: add mask and unmask interrupt APIs
Date: Wed, 17 Jul 2019 08:45:46 +0000 [thread overview]
Message-ID: <MWHPR11MB18395EC11DFB036797408BFCBFC90@MWHPR11MB1839.namprd11.prod.outlook.com> (raw)
In-Reply-To: <BYAPR18MB2424ED7AEB7544B114409F61C8C90@BYAPR18MB2424.namprd18.prod.outlook.com>
> -----Original Message-----
> From: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
> Sent: Wednesday, July 17, 2019 5:03 PM
> To: Hyong Youb Kim (hyonkim) <hyonkim@cisco.com>; Nithin Kumar
> Dabilpuram <ndabilpuram@marvell.com>; David Marchand
> <david.marchand@redhat.com>; Thomas Monjalon
> <thomas@monjalon.net>; Ferruh Yigit <ferruh.yigit@intel.com>; Bruce
> Richardson <bruce.richardson@intel.com>
> Cc: John Daley (johndale) <johndale@cisco.com>; Shahed Shaikh
> <shshaikh@marvell.com>; dev@dpdk.org
> Subject: RE: [RFC PATCH v3 2/3] eal: add mask and unmask interrupt APIs
>
> > > > -----Original Message-----
> > > > From: Hyong Youb Kim (hyonkim) <hyonkim@cisco.com>
> > > > Sent: Wednesday, July 17, 2019 11:26 AM
> > > > To: Nithin Kumar Dabilpuram <ndabilpuram@marvell.com>; David
> > > Marchand
> > > > <david.marchand@redhat.com>; Thomas Monjalon
> > <thomas@monjalon.net>;
> > > > Ferruh Yigit <ferruh.yigit@intel.com>; Bruce Richardson
> > > > <bruce.richardson@intel.com>
> > > > Cc: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; John Daley
> > > > (johndale) <johndale@cisco.com>; Shahed Shaikh
> > > > <shshaikh@marvell.com>; dev@dpdk.org
> > > > Subject: RE: [RFC PATCH v3 2/3] eal: add mask and unmask interrupt
> > > > APIs
> > > > > +rte_intr_mask(const struct rte_intr_handle *intr_handle) {
> > > > > + if (intr_handle && intr_handle->type ==
> RTE_INTR_HANDLE_VDEV)
> > > > > + return 0;
> > > > > +
> > > > > + if (!intr_handle || intr_handle->fd < 0 ||
> > > > > +intr_handle->uio_cfg_fd <
> > > > 0)
> > > > > + return -1;
> > > > > +
> > > > > + switch (intr_handle->type){
> > > > > + /* Both masking and disabling are same for UIO */
> > > > > + case RTE_INTR_HANDLE_UIO:
> > > > > + if (uio_intr_disable(intr_handle))
> > > > > + return -1;
> > > > > + break;
> > > > > + case RTE_INTR_HANDLE_UIO_INTX:
> > > > > + if (uio_intx_intr_disable(intr_handle))
> > > > > + return -1;
> > > > > + break;
> > > > > + /* not used at this moment */
> > > > > + case RTE_INTR_HANDLE_ALARM:
> > > > > + return -1;
> > > > > +#ifdef VFIO_PRESENT
> > > > > + case RTE_INTR_HANDLE_VFIO_MSIX:
> > > > > + case RTE_INTR_HANDLE_VFIO_MSI:
> > > > > + return 0;
> > > >
> > > > Isn't this a little confusing? It returns success, but irq is not masked.
> > >
> > > Yes. How about changing the API to rte_intr_ack()(Acknowledge the
> > > interrupt)
> > > Or something similar? i.e replace rte_intr_unmask() with
> > > rte_intr_ack() for this use case.
> > >
> >
> > Not sure. I do not have a good suggestion here :-) Like to hear from
> > David when he comes back, as he spent most time on this issue..
>
> Sure. He is on vacation.
> Any reason for thinking, rte_intr_ack() may not be semantically correct?
> I think, it is very much correct if there are no better suggestions.
> Anyway it the name, From VFIO perspective, we know what is expected so I
> think it is fine.
>
> >
> > Why not return -1 and let the caller deal with it?
>
> If we make it as rte_intr_ack() no need to return -1 for MSIX-VFIO+Linux
> as it is semantically correct.
>
Ack can be ambiguous. For INTx, ack usually means PIO to a NIC
register, saying "I got your interrupt, please de-assert irq".
Besides the name, are we agreeing that we want these?
- Unmask if INTx
- Nothing if MSI/MSI-X
So, really just "unmask if INTx". I am ok with rte_intr_unmask() if we
make this intention clear. rte_unmask_if_intx() looks messy.
Thanks..
-Hyong
> >
> > Optimist view:
> > Maintainers will see the error as vfio-pci + MSI/MSI_X is on
> > everyone's test list. And it forces them to confront the issue. Do I
> > really need unmask here, etc.
>
> If we make it as ack then it fine as driver does not need to know the fine
> details.
>
> >
> > Pessimist view:
> > Wastes a lot of people's time. Potentially duplicate code like this
> > everywhere.
> >
> > if (INTx) unmask();
> >
> > BTW, are you targeting 19.08 or 19.11? Not sure how much change we can
> > tolerate in 19.08.
>
>
> 19.08 as fundamentally it correct. Finer adjustment can made by existing
> drivers if required in the testing phase.
>
> It is trivial change as scope is limited to interrupt hander rte_intr_enable()
> replacement with rte_intr_ack(). For MSIX case, it should be real NOP,
> so I don't think there issue. It should be much better than the existing
> state, where almost everything broken.
>
> > Requirements for 19.08 seem to be...
> > - Must fix the redhat bz (lost interrupt issue with qede + MSI/MSI-X)
> > - Fix potentially similar issues in other drivers too?
>
> Proposed patch will fix the above mentioned issues.
>
> >
> > Thanks..
> > -Hyong
> >
> > > > As is, return code 0 means...
> > > > - igb_uio: irq is masked for INTx, MSI, MSI-X
> > > > - vfio-pci + INTx: irq is masked
> > > > - vfio-pci + MSI/MSI-X: no changes
> > > >
> > > > Masking is useful only for INTx, IMO...
> > > >
> > > > Masking MSI/MSI-X via PCI-defined mechanisms (e.g. Mask bit in MSI-X
> > > > Table) has no practical use for drivers.
> Handshaking/masking/unmasking
> > is
> > > > done via device/vendor specific ways, as needed. See all those
> > > > ack/block/unblock/credit/... mechanisms used in various drivers/NICs
> to
> > > > control interrupts their own way.
> > > >
> > > > A long time ago in early PCIe days, the linux kernel did auto-masking for
> > > > MSI/MSI-X (i.e. mask before calling netdev irq handler). It was soon
> > > removed
> > > > as it was unnecessary overhead (expensive PIOs to NIC for every
> > interrupt).
> > > > Windows and FreeBSD do not do auto-masking either.
> > >
> > > rte_intr_ack() can abstract FreeBSD and Windows difference.
> > >
next prev parent reply other threads:[~2019-07-17 8:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-15 16:50 [dpdk-dev] [RFC PATCH] vfio: avoid re-installing irq handler Jerin Jacob Kollanukkaran
2019-07-16 5:58 ` Hyong Youb Kim (hyonkim)
2019-07-16 6:47 ` Jerin Jacob Kollanukkaran
2019-07-16 7:49 ` Hyong Youb Kim (hyonkim)
2019-07-16 9:56 ` Jerin Jacob Kollanukkaran
2019-07-16 6:46 ` [dpdk-dev] [RFC PATCH] eal: add mask and unmask interrupt apis Nithin Dabilpuram
2019-07-16 7:01 ` [dpdk-dev] [RFC PATCH v2] " Nithin Dabilpuram
2019-07-16 16:44 ` [dpdk-dev] [RFC PATCH v3 1/3] vfio: revert change that does intr eventfd setup at probe Nithin Dabilpuram
2019-07-16 16:44 ` [dpdk-dev] [RFC PATCH v3 2/3] eal: add mask and unmask interrupt APIs Nithin Dabilpuram
2019-07-17 5:55 ` Hyong Youb Kim (hyonkim)
2019-07-17 6:14 ` Jerin Jacob Kollanukkaran
2019-07-17 7:09 ` Hyong Youb Kim (hyonkim)
2019-07-17 8:03 ` Jerin Jacob Kollanukkaran
2019-07-17 8:45 ` Hyong Youb Kim (hyonkim) [this message]
2019-07-17 9:20 ` Jerin Jacob Kollanukkaran
2019-07-17 9:51 ` Hyong Youb Kim (hyonkim)
2019-07-17 10:43 ` Jerin Jacob Kollanukkaran
2019-07-17 11:06 ` Hyong Youb Kim (hyonkim)
2019-07-17 11:16 ` Jerin Jacob Kollanukkaran
2019-07-17 12:04 ` Nithin Kumar Dabilpuram
2019-07-16 16:44 ` [dpdk-dev] [RFC PATCH v3 3/3] drivers/net: use unmask API in interrupt handlers Nithin Dabilpuram
2019-07-17 6:01 ` Hyong Youb Kim (hyonkim)
2019-07-17 7:47 ` Nithin Kumar Dabilpuram
2019-07-16 20:06 ` [dpdk-dev] [RFC PATCH v3 1/3] vfio: revert change that does intr eventfd setup at probe Stephen Hemminger
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=MWHPR11MB18395EC11DFB036797408BFCBFC90@MWHPR11MB1839.namprd11.prod.outlook.com \
--to=hyonkim@cisco.com \
--cc=bruce.richardson@intel.com \
--cc=david.marchand@redhat.com \
--cc=dev@dpdk.org \
--cc=ferruh.yigit@intel.com \
--cc=jerinj@marvell.com \
--cc=johndale@cisco.com \
--cc=ndabilpuram@marvell.com \
--cc=shshaikh@marvell.com \
--cc=thomas@monjalon.net \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).