From: Avi Kivity <avi@scylladb.com>
To: Greg KH <gregkh@linuxfoundation.org>,
Vlad Zolotarov <vladz@cloudius-systems.com>
Cc: linux-kernel@vger.kernel.org, mst@redhat.com, hjk@hansjkoch.de,
corbet@lwn.net, bruce.richardson@intel.com,
avi@cloudius-systems.com, gleb@cloudius-systems.com,
stephen@networkplumber.org, alexander.duyck@gmail.com
Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support
Date: Mon, 5 Oct 2015 14:09:32 +0300 [thread overview]
Message-ID: <56125A6C.7030107@scylladb.com> (raw)
In-Reply-To: <20151005105715.GA23459@kroah.com>
On 10/05/2015 01:57 PM, Greg KH wrote:
> On Mon, Oct 05, 2015 at 01:48:39PM +0300, Vlad Zolotarov wrote:
>>
>> On 10/05/15 10:56, Greg KH wrote:
>>> On Mon, Oct 05, 2015 at 10:41:39AM +0300, Vlad Zolotarov wrote:
>>>>>> +struct msix_info {
>>>>>> + int num_irqs;
>>>>>> + struct msix_entry *table;
>>>>>> + struct uio_msix_irq_ctx {
>>>>>> + struct eventfd_ctx *trigger; /* MSI-x vector to eventfd */
>>>>> Why are you using eventfd for msi vectors? What's the reason for
>>>>> needing this?
>>>> A small correction - for MSI-X vectors. There may be only one MSI vector per
>>>> PCI function and if it's used it would use the same interface as a legacy
>>>> INT#x interrupt uses at the moment.
>>>> So, for MSI-X case the reason is that there may be (in most cases there will
>>>> be) more than one interrupt vector. Thus, as I've explained in a PATCH1
>>>> thread we need a way to indicated each of them separately. eventfd seems
>>>> like a good way of doing so. If u have better ideas, pls., share.
>>> You need to document what you are doing here, I don't see any
>>> explaination for using eventfd at all.
>>>
>>> And no, I don't know of any other solution as I don't know what you are
>>> trying to do here (hint, the changelog didn't document it...)
>>>
>>>>> You haven't documented how this api works at all, you are going to have
>>>>> to a lot more work to justify this, as this greatly increases the
>>>>> complexity of the user/kernel api in unknown ways.
>>>> I actually do documented it a bit. Pls., check PATCH3 out.
>>> That provided no information at all about how to use the api.
>>>
>>> If it did, you would see that your api is broken for 32/64bit kernels
>>> and will fall over into nasty pieces the first time you try to use it
>>> there, which means it hasn't been tested at all :(
>> It has been tested of course ;)
>> I tested it only in 64 bit environment however where both kernel and user
>> space applications were compiled on the same machine with the same compiler
>> and it could be that "int" had the same number of bytes both in kernel and
>> in user space application. Therefore it worked perfectly - I patched DPDK to
>> use the new uio_pci_generic MSI-X API to test this and I have verified that
>> all 3 interrupt modes work: MSI-X with SR-IOV VF device in Amazon EC2 guest
>> and INT#x and MSI with a PF device on bare metal server.
>>
>> However I agree using uint32_t for "vec" and "fd" would be much more
>> correct.
> I don't think file descriptors are __u32 on a 64bit arch, are they?
>
> And NEVER use the _t types in kernel code, the namespaces is all wrong
> and it is not applicable for us, sorry.
Wasn't the real reason that they aren't defined (or reserved) by C89,
and therefore could clash with a user identifier, rather than some
inherent wrongness?
next prev parent reply other threads:[~2015-10-05 11:09 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-04 20:43 [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver Vlad Zolotarov
2015-10-04 20:43 ` [PATCH v3 1/3] uio: add ioctl support Vlad Zolotarov
2015-10-05 3:03 ` Greg KH
2015-10-05 7:33 ` Vlad Zolotarov
2015-10-05 8:01 ` Greg KH
2015-10-05 10:36 ` Vlad Zolotarov
2015-10-05 20:02 ` Michael S. Tsirkin
[not found] ` <CAOYyTHZ2=UCYxuJKvd5S6qxp=84DBq5bMadg5wL0rFLZBh2-8Q@mail.gmail.com>
2015-10-05 22:29 ` Michael S. Tsirkin
2015-10-06 8:33 ` Vlad Zolotarov
2015-10-06 14:19 ` Michael S. Tsirkin
2015-10-06 14:30 ` Gleb Natapov
2015-10-06 15:19 ` Michael S. Tsirkin
2015-10-06 15:31 ` Vlad Zolotarov
2015-10-06 15:57 ` Gleb Natapov
2015-10-04 20:43 ` [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov
2015-10-05 3:11 ` Greg KH
2015-10-05 7:41 ` Vlad Zolotarov
2015-10-05 7:56 ` Greg KH
2015-10-05 10:48 ` Vlad Zolotarov
2015-10-05 10:57 ` Greg KH
2015-10-05 11:09 ` Avi Kivity [this message]
2015-10-05 13:08 ` Greg KH
2015-10-05 11:41 ` Vlad Zolotarov
2015-10-05 11:47 ` Avi Kivity
2015-10-05 11:53 ` Vlad Zolotarov
2015-10-05 8:28 ` Avi Kivity
2015-10-05 9:49 ` Greg KH
2015-10-05 10:20 ` Avi Kivity
2015-10-06 14:38 ` Michael S. Tsirkin
2015-10-06 14:43 ` Vlad Zolotarov
2015-10-06 14:56 ` Michael S. Tsirkin
2015-10-06 15:23 ` Avi Kivity
2015-10-06 18:51 ` Alex Williamson
2015-10-06 21:32 ` Stephen Hemminger
2015-10-06 21:41 ` Alex Williamson
[not found] ` <CAOaVG152OrQz-Bbnpr0VeE+vLH7nMGsG6A3sD7eTQHormNGVUg@mail.gmail.com>
2015-10-07 7:57 ` Vlad Zolotarov
[not found] ` <5614C160.6000203@scylladb.com>
2015-10-07 8:00 ` Vlad Zolotarov
2015-10-07 8:01 ` Vlad Zolotarov
2015-10-07 6:52 ` Avi Kivity
2015-10-07 16:31 ` Alex Williamson
2015-10-07 16:39 ` Avi Kivity
2015-10-07 21:05 ` Michael S. Tsirkin
2015-10-08 4:19 ` Gleb Natapov
2015-10-08 7:41 ` Michael S. Tsirkin
2015-10-08 7:59 ` Gleb Natapov
2015-10-08 9:38 ` Michael S. Tsirkin
2015-10-08 9:45 ` Gleb Natapov
2015-10-08 12:15 ` Michael S. Tsirkin
2015-10-08 5:33 ` Avi Kivity
2015-10-08 7:32 ` Michael S. Tsirkin
2015-10-08 8:46 ` Avi Kivity
2015-10-08 9:16 ` Michael S. Tsirkin
2015-10-08 9:44 ` Avi Kivity
2015-10-08 12:06 ` Michael S. Tsirkin
2015-10-08 12:27 ` Gleb Natapov
2015-10-08 13:20 ` Michael S. Tsirkin
2015-10-08 13:28 ` Gleb Natapov
2015-10-08 16:43 ` Michael S. Tsirkin
2015-10-08 17:01 ` Gleb Natapov
2015-10-08 17:39 ` Michael S. Tsirkin
2015-10-08 17:53 ` Gleb Natapov
2015-10-08 18:38 ` Greg KH
2015-10-08 8:32 ` Michael S. Tsirkin
2015-10-08 8:52 ` Gleb Natapov
2015-10-08 9:19 ` Avi Kivity
2015-10-08 10:26 ` Michael S. Tsirkin
2015-10-08 13:20 ` Avi Kivity
2015-10-08 14:17 ` Michael S. Tsirkin
2015-10-08 15:31 ` Alex Williamson
2015-10-07 20:05 ` Michael S. Tsirkin
2015-10-07 7:55 ` Vlad Zolotarov
2015-10-08 8:48 ` Michael S. Tsirkin
2015-10-06 15:28 ` Vlad Zolotarov
2015-10-06 14:46 ` Michael S. Tsirkin
2015-10-06 15:27 ` Avi Kivity
2015-10-05 8:41 ` Stephen Hemminger
2015-10-05 9:08 ` Vlad Zolotarov
2015-10-05 10:06 ` Vlad Zolotarov
2015-10-05 20:09 ` Michael S. Tsirkin
2015-10-05 9:11 ` Vlad Zolotarov
2015-10-05 19:16 ` Michael S. Tsirkin
2015-10-04 20:43 ` [PATCH v3 3/3] Documentation: update uio-howto Vlad Zolotarov
2015-10-04 20:45 ` [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver Vlad Zolotarov
2015-10-05 19:50 ` Michael S. Tsirkin
2015-10-06 8:37 ` Vlad Zolotarov
2015-10-06 14:30 ` Michael S. Tsirkin
2015-10-06 14:40 ` Vlad Zolotarov
2015-10-06 15:13 ` Michael S. Tsirkin
2015-10-06 16:35 ` Vlad Zolotarov
2015-10-06 15:11 ` Avi Kivity
2015-10-06 15:15 ` Michael S. Tsirkin
2015-10-06 16:00 ` Gleb Natapov
2015-10-06 16:09 ` Avi Kivity
2015-10-07 10:25 ` Michael S. Tsirkin
2015-10-07 10:28 ` Avi Kivity
-- strict thread matches above, loose matches on Subject: below --
2015-10-04 20:39 Vlad Zolotarov
2015-10-04 20:39 ` [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov
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