On Mon, Jun 4, 2012 at 7:37 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote: > On Sun, Jun 3, 2012 at 6:05 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: >> On Fri, Jun 1, 2012 at 4:30 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote: >>> On Tue, May 29, 2012 at 1:50 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote: >>>> >>>> The bus-side address space should not be more than 32 bits no matter >>>> what. As Bjorn indicates, you seem to be mixing up bus and cpu >>>> addresses all over the place. >>> >>> please check update patches that is using converted pci bus address >>> for boundary checking. >> >> What problem does this fix? There's significant risk that this >> allocation change will make us trip over something, so it must fix >> something to make it worth considering. > > If we do not enable that, we would not find the problem. Sorry, that didn't make any sense to me. I'm hoping you will point us to a bug report that is fixed by this patch. > On one my test setup that _CRS does state 64bit resource range, > but when I clear some device resource manually and let kernel allocate > high, just then find out those devices does not work with drivers. > It turns out _CRS have more big range than what the chipset setting states. > with fixing in BIOS, allocate high is working now on that platform. I didn't understand this either, sorry. Are you saying that this patch helps us work around a BIOS defect? >> Steve's problem doesn't count because that's a "pci=nocrs" case that >> will always require special handling. > > but pci=nocrs is still supported, even some systems does not work with > pci=use_crs > >> A general solution is not >> possible without a BIOS change (to describe >4GB apertures) or a >> native host bridge driver (to discover >4GB apertures from the >> hardware). These patches only make Steve's machine work by accident >> -- they make us put the video device above 4GB, and we're just lucky >> that the host bridge claims that region. > > Some bios looks enabling the non-stated range default to legacy chain. > Some bios does not do that. only stated range count. > So with pci=nocrs we still have some chance to get allocate high working. The patch as proposed changes behavior for all systems, whether we're using _CRS or not (in fact, it even changes the behavior for non-x86 systems). The only case we know of where it fixes something is Steve's system, where he already has to use "pci=nocrs" in order for it to help. My point is that it would be safer to leave things as they are for everybody, and merely ask Steve to use "pci=nocrs pci=alloc_high" or something similar. >> One possibility is some sort of boot-time option to force a PCI device >> to a specified address. That would be useful for debugging as well as >> for Steve's machine. > > yeah, how about > > pci=alloc_high > > and default to disabled ? I was actually thinking of something more specific, e.g., a way to place one device at an exact address. I've implemented that a couple times already for testing various things. But maybe a more general option like "pci=alloc_high" would make sense, too. Linux has a long history of allocating bottom-up. Windows has a long history of allocating top-down. You're proposing a third alternative, allocating bottom-up starting at 4GB for 64-bit BARs. If we change this area, I would prefer something that follows Windows because I think it will be closer to what's been tested by Windows. Do you think your alternative is better? -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
