On Mon, Nov 15, 2021 at 08:18:53AM +0100, Thomas Hellström wrote: > On 11/14/21 22:19, Linus Torvalds wrote: > > On Sun, Nov 14, 2021 at 1:00 PM Dave Airlie <airlied@xxxxxxxxx> wrote: > > > i915 will no longer be x86-64 only in theory, since Intel now produces > > > PCIe graphics cards using the same hw designs. > > Well, at least in my tree, it still has the "depends on X86", along > > with several other x86-only things (like "select INTEL_GTT", which is > > also x86-only) Yeah it's work in progress and 12+ years of x86 pile up high&deep aren't easy to fix. So please assume the depends on X86 is gone already (and select INTEL_GTT is optional, it's only needed for igfx older than about 8 years or so), but we can't do that yet because all the build boots would run out of air screaming so much :-) > > So by the time that non-x86 theory becomes reality, hopefully the i915 > > people will also have figured out how to do the cache flushing > > properly. > > > > And hopefully that "do it properly" ends up being simply that the > > particular configuration that ends up being portable simply doesn't > > need to do it at all and can statically just not build it, > > sidestepping the issue entirely. > > > > Fingers crossed. > > For non-x86 / discrete graphics, plan is only coherent mappings, although > the "Just not build it" part hasn't been properly figured out yet I guess. > But point taken. Yeah for non-x86 it'll be standard dma-api all the way down. For x86 that ship sailed long ago, but also I'm not clear on why we added a new cache flush primitive for that instead of just continuing to use clflush like we've done since forever. For x86 integrated gpu we _know_ which cpu is there, clflush will exist. So any new horrors shouldn't be needed, not sure why a wbinvd_on_all_cpus slipped in. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
