Messages in this thread | | | Date | Tue, 5 Feb 2019 07:39:06 -0700 | From | Keith Busch <> | Subject | Re: [PATCH] nvme: Enable acceleration feature of A64FX processor |
| |
On Tue, Feb 05, 2019 at 09:56:05PM +0900, Takao Indoh wrote: > On Fri, Feb 01, 2019 at 07:54:14AM -0700, Keith Busch wrote: > > On Fri, Feb 01, 2019 at 09:46:15PM +0900, Takao Indoh wrote: > > > From: Takao Indoh <indou.takao@fujitsu.com> > > > > > > Fujitsu A64FX processor has a feature to accelerate data transfer of > > > internal bus by relaxed ordering. It is enabled when the bit 56 of dma > > > address is set to 1. > > > > Wait, what? RO is a standard PCIe TLP attribute. Why would we need this? > > I should have explained this patch more carefully. > > Standard PCIe devices can use Relaxed Ordering (RO) by setting Attr > field in the TLP header, however, this mechanism cannot be utilized if > the device does not support RO feature. Fujitsu A64FX processor has an > alternate feature to enable RO in its Root Port by setting the bit 56 of > DMA address. This mechanism enables to utilize RO feature even if the > device does not support standard PCIe RO.
I think you're better of just purchasing devices that support the capability per spec rather than with a non-standard work around.
| |