Re: scsipi: physio split the request

[Jaromír Doleček <jaromir.dolecek%gmail.com@localhost>]

Le jeu. 27 déc. 2018 à 15:41, Emmanuel Dreyfus <manu%netbsd.org@localhost> a écrit :
>
> On Thu, Dec 27, 2018 at 02:33:28PM +0000, Christos Zoulas wrote:
> > I think you need resurrect the tls-maxphys branch... It was close to working
> > IIRC.
>
> What happens if I just #define MAXPHYS (1024*1204*1024) ?

Several drivers use MAXPHYS to allocate DMA memory for them (e.g.
nvme), they usually try to allocate
MAXPHYS * (max number of scatter-gather vectors). These will either
fail, or block huge amounts of RAM.

Also it just happens to be hard I/O size limit for ISA, and ATA/IDE
drives not supporting LBA48.

Even for hw which does support bigger I/O (stuff behind PCI, SCSI, ATA
drivers with LBA48), the drivers might be buggy and not cope.

Nothing good happens out of this, unfortunately the lower layers need
to be fixed first.

Jaromir