On Tue, Oct 06, 2020 at 07:29:16AM -0700, Bart Van Assche wrote:
> On 9/24/20 4:49 AM, Jason Gunthorpe wrote:
> > On Thu, Sep 24, 2020 at 06:49:07AM +0100, Christoph Hellwig wrote:
> > > > > > + } else {
> > > > > > + device->dev.dma_parms = dma_device->dma_parms;
> > > > > > /*
> > > > > > + * Auto setup the segment size if a DMA device was passed in.
> > > > > > + * The PCI core sets the maximum segment size to 64 KB. Increase
> > > > > > + * this parameter to 2 GB.
> > > > > > */
> > > > > > + dma_set_max_seg_size(dma_device, SZ_2G);
> > > > >
> > > > > You can't just inherity DMA properties like this this. Please
> > > > > fix all code that looks at the seg size to look at the DMA device.
> > > >
> > > > Inherit? This is overriding the PCI default of 64K to be 2G for RDMA
> > > > devices.
> > >
> > > With inherit I mean the
> > >
> > > device->dev.dma_parms = dma_device->dma_parms;
> > >
> > > line, which is completely bogus. All DMA mapping is done on the
> > > dma_device in the RDMA core and ULPs, so it also can't have an effect.
> >
> > Oh. Yes, no idea why that is there..
> >
> > commit c9121262d57b8a3be4f08073546436ba0128ca6a
> > Author: Bart Van Assche <bvanassche@xxxxxxx>
> > Date: Fri Oct 25 15:58:30 2019 -0700
> >
> > RDMA/core: Set DMA parameters correctly
> > The dma_set_max_seg_size() call in setup_dma_device() does not have any
> > effect since device->dev.dma_parms is NULL. Fix this by initializing
> > device->dev.dma_parms first.
> >
> > Bart?
>
> (just noticed this email)
>
> Hi Jason,
>
> That code may be a leftover from when the ib_dma_*() functions used &dev->dev as
> their first argument instead of dev->dma_device.
Hmm the above was two years after the commit that added dma_device? I
assumed you added this because you were doing testing with rxe?
Jason
