linux-kernel - Re: [PATCH v5 0/4] uio: add MSI/MSI-X support to uio_pci

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Message-ID: <5614308F.3040903@cloudius-systems.com>
Date:	Tue, 6 Oct 2015 23:35:27 +0300
From:	Vlad Zolotarov <vladz@...udius-systems.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, hjk@...sjkoch.de, corbet@....net,
	gregkh@...uxfoundation.org, bruce.richardson@...el.com,
	avi@...udius-systems.com, gleb@...udius-systems.com,
	stephen@...workplumber.org, alexander.duyck@...il.com
Subject: Re: [PATCH v5 0/4] uio: add MSI/MSI-X support to uio_pci_generic
 driver



On 10/06/15 21:27, Michael S. Tsirkin wrote:
> On Tue, Oct 06, 2015 at 08:17:35PM +0300, Vlad Zolotarov wrote:
>> This series add support for MSI and MSI-X interrupts to uio_pci_generic driver.
>>
>> Currently uio_pci_generic demands INT#x interrupts source be available. However
>> there are devices that simply don't have INT#x capability, for instance SR-IOV
>> VF devices that simply don't have INT#x capability. For such devices
>> uio_pci_generic will simply fail (more specifically its probe() will fail).
>>
>> When IOMMU is either not available (e.g. Amazon EC2) or not acceptable due to
>> performance overhead and thus VFIO is not an option users that develop
>> user-space drivers are left without any option but to develop some proprietary
>> UIO drivers (e.g. igb_uio driver in Intel's DPDK) just to be able to use UIO
>> infrastructure.
>>
>> This series provides a generic solution for this problem while preserving the
>> original behaviour for devices for which the original uio_pci_generic had worked
>> before (i.e. INT#x will be used by default).
>>
>> New in v5:
>>     - Expanded the commitlog on PATCH1.
> Looks like you didn't attempt to address any of my review comments.
> I don't intend to review this until you do.

So far there hasn't been any comments related to the code in these 
patches  from your side but rather comments about the general flaws of 
the current uio_pci_generic in particular and UIO in general that have 
nothing to do with this series. Therefore obviously there was nothing to 
address.
If u have any comments related to _THIS_ series I'd be glad to address. 
So far I was under the strong impression that u develop an obviously 
theoretical discussion about "nice to have fixed" stuff in UIO, which 
was obvious to everybody on this thread had nothing to do with this 
patch series.

Could it be that I've got u wrong? If so, could u, pls., clarify what 
u'd like me to fix in these patches exactly and why?

thanks,
vlad

>
>> New in v4:
>>     - Use portable __u32 and __s32 types from asm/types.h for
>>       defining uio_pci_generic_irq_set fields.
>>     - Use proper _IO macros for defining read and write ioctl()
>>       commands.
>>     - Moved bars mapping setting into a separate patch.
>>     - Update uio_pci_generic example in uio-howto.tmpl.
>>
>> New in v3:
>>     - Add __iomem qualifier to temp buffer receiving ioremap value.
>>   
>> New in v2:
>>     - Added #include <linux/uaccess.h> to uio_pci_generic.c
>>
>>
>> Vlad Zolotarov (4):
>>    uio: add ioctl support
>>    uio_pci_generic: properly initialize PCI bars mappings towards UIO
>>    uio_pci_generic: add MSI/MSI-X support
>>    Documentation: update uio-howto
>>
>>   Documentation/DocBook/uio-howto.tmpl | 139 ++++++++++--
>>   drivers/uio/uio.c                    |  15 ++
>>   drivers/uio/uio_pci_generic.c        | 409 +++++++++++++++++++++++++++++++++--
>>   include/linux/uio_driver.h           |   3 +
>>   include/uapi/linux/uio_pci_generic.h |  51 +++++
>>   5 files changed, 574 insertions(+), 43 deletions(-)
>>   create mode 100644 include/uapi/linux/uio_pci_generic.h
>>
>> -- 
>> 2.1.0

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