Hi Bryan I want to make sure I get the right message for Bjorn, so held off on sending anything before confirming. As far as clearing the 64-bit resource flag when it's a 32-bit address, that seems pretty straight forward as captured in the comment. But do we actually rely on a memory window below 4GB? If the memory window is above 4GB, we just won't be able to support devices with 32-bit BARs there, but is that a concern? Should the comment just say that if the window is assigned >4GB, we simply won't be able to support 32-bit BAR devices on that domain, and that's 'ok'? Thanks, Keith On Thu, Feb 25, 2016 at 08:42:19AM -0600, Bjorn Helgaas wrote: > On Tue, Feb 23, 2016 at 06:24:00PM +0000, Keith Busch wrote: > > On Mon, Feb 22, 2016 at 04:10:24PM -0600, Bjorn Helgaas wrote: > > > I'm not sure how to deal with the question of a hot-added VMD. Maybe > > > all we can do now is add a comment to the effect that we assume BIOS > > > has assigned the non-prefetchable BAR below 4GB, and if Linux assigns > > > that BAR for hot-added VMDs, that assumption will likely break. > > > > Yes, we can assume BIOS always assigns. There are other BIOS dependencies > > in order for the host to see the h/w as a VMD endpoint. > > > > > diff --git a/arch/x86/pci/vmd.c b/arch/x86/pci/vmd.c > > > index d57e480..7554722 100644 > > > --- a/arch/x86/pci/vmd.c > > > +++ b/arch/x86/pci/vmd.c > > > @@ -532,6 +532,16 @@ static int vmd_enable_domain(struct vmd_dev *vmd) > > > .flags = IORESOURCE_BUS | IORESOURCE_PCI_FIXED, > > > }; > > > > > > + /* > > > + * If the window is below 4GB, clear IORESOURCE_MEM_64 so we can > > > + * put 32-bit resources in the window. > > > + * > > > + * There's no hardware reason why a 64-bit window *couldn't* > > > + * contain a 32-bit resource, but pbus_size_mem() computes the > > > + * bridge window size assuming a 64-bit window will contain no > > > + * 32-bit resources. __pci_assign_resource() enforces that > > > + * artificial restriction to make sure everything will fit. > > > + */ > > > > This sounds good to me. Thanks! > > > > > res = &vmd->dev->resource[VMD_MEMBAR1]; > > > upper_bits = upper_32_bits(res->end); > > > flags = res->flags & ~IORESOURCE_SIZEALIGN; > > Can you prepare a patch, that adds both comments, please? (The one > about how we assume BIOS assigns the BAR below 4GB, and the one I > drafted above.) -- 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
