Messages in this thread | | | Date | Sun, 1 Oct 2023 07:22:36 -0700 | From | Jerry Snitselaar <> | Subject | Re: [PATCH 3/3] cnic,bnx2,bnx2x: use UIO_MEM_DMA_COHERENT |
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On Sun, Oct 01, 2023 at 01:57:25PM +0200, Greg Kroah-Hartman wrote: > On Sun, Oct 01, 2023 at 12:44:05PM +0200, Hannes Reinecke wrote: > > On 9/30/23 20:28, Greg Kroah-Hartman wrote: > > > On Sat, Sep 30, 2023 at 11:19:20AM -0700, Chris Leech wrote: > > > > On Sat, Sep 30, 2023 at 09:06:51AM +0200, Greg Kroah-Hartman wrote: > > > > > On Fri, Sep 29, 2023 at 10:00:23AM -0700, Chris Leech wrote: > > > > > > Make use of the new UIO_MEM_DMA_COHERENT type to properly handle mmap > > > > > > for dma_alloc_coherent buffers. > > > > > > > > > > Why are ethernet drivers messing around with UIO devices? That's not > > > > > what UIO is for, unless you are trying to do kernel bypass for these > > > > > devices without anyone noticing? > > > > > > > > > > confused, > > > > > > > > It's confusing. The bnx2 driver stack included a cnic (converged nic?) > > > > module that sits between the ethernet drivers (bnx2, bnx2x) and protocol > > > > offload drivers (iscsi, fcoe, rdma). > > > > > > > > The iscsi module (bnx2i) uses a passthrough interface from cnic to > > > > handle some network configuration that the device firmware doesn't do. > > > > It uses a uio device and a userspace component called iscsiuio to do > > > > that. > > > > > > That's horrible, and not what the UIO api is for at all. Configure the > > > device like any other normal kernel device, don't poke at raw memory > > > values directly, that way lies madness. > > > > > > Have a pointer to the userspace tool anywhere? All I found looks like a > > > full IP stack in userspace under that name, and surely that's not what > > > this api is for... > > > > > But that's how the interface is used, in particular for the bnx2i driver. > > Problem is that the bnx2i iSCSI offload is just that, an iSCSI offload. Not > > a TCP offload. So if the iSCSI interface is configured to > > acquire the IP address via DHCP, someone has to run the DHCP protocol. > > But the iSCSI offload can't, and the bnx2i PCI device is not a network > > device so that the normal network stack can't be used. > > And so the architects of the bnx2i card decided to use UIO to pass > > the network traffic to userspace, and used the userspace 'iscsiuio' > > application to run DHCP in userspace. > > > > But's been that way for several years now; so long, in fact, that > > the card itself has been out of support from Marvell (since quite some > > years, too, IIRC). And even the successor of that card (the qedi driver) > > is nearing EOL. Mind you, the qedi driver is using the same interface (by > > using UIO to run DHCP in userspace), so singling out the bnx2i for bad > > design can be construed as being unfair :-) > > Ok, let's say they are all horrible! :) > > > I agree, though, that the design is a mess. > > Ok, so why are we papering over it and continuing to allow it to exist? > > What "broke" to suddenly require this UIO change? If this has been > around for a very long time, what has caused this to now require the UIO > layer to change? > > thanks, > > greg k-h
Changes last year to the dma-mapping api to no longer allow __GFP_COMP, in particular these two (from the e529d3507a93 dma-mapping pull for 6.2):
ffcb75458460 dma-mapping: reject __GFP_COMP in dma_alloc_attrs | 2022-11-21 | (Christoph Hellwig) bb73955c0b1d cnic: don't pass bogus GFP_ flags to dma_alloc_coherent | 2022-11-21 | (Christoph Hellwig)
Regards, Jerry
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