On Wed, Mar 16, 2016 at 04:49:00PM +1100, Alexey Kardashevskiy wrote: > On 03/16/2016 04:10 PM, Eli Cohen wrote: > >On Wed, Mar 16, 2016 at 01:07:58PM +1100, Alexey Kardashevskiy wrote: > >> > >>So with v4.5 as a host, there is no actual distro available today to > >>use as a guest in the next 6 months (or whatever it takes to > >>backport this partucular patch back there). > >> > >>You could have added a module parameter to enforce the old behavoir, > >>at least... > >> > >>And sorry but from the original commit log I could not understand > >>why exactly all existing guests need to be broken. Could you please > >>point me to a piece of documentation describing all this UAR > >>bisuness (what is UAR, why 128 UARs are required and for what, etc). > >>Thanks. > >> > > > >We are going to send a patch that fixes this using a module parameter. > >The patch will be on top of Huy's patch. > > > >Some background to the problem: mlx4 supported devices require 128 UAR > > What does UAR stand for? User Access Region. It's the way you interface with the hardware. > > >pages from PCI memory space defined by BAR2-3. Each UAR page can be > >any power of 2 value from 4K up to 64K. Before Huy's patch the driver > >chose UAR page size to be equal to system page size. Since PowerPC's > >page size is 64K this means minimum requirement of UAR pages is not > >met (default UAR BAR is 8MB and only half of it is really reserved for > >UARs). > > And what was the downside? afaict the performance was good... >
It's not a performance issue. Defining 64KB for a UAR is not required and wastes pci memory mapped i/o space. > > >More details can be found in the programmer's manual. > > Can you please point me to this manual on the website? I tried, > honestly, could not find it. Thanks. > It's not publically available. If you have an FAE that work with your company you can ask him how to get the doc. > > -- > Alexey > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
