Re: [PATCHv8 0/5] Driver for new "VMD" device
From: Bjorn Helgaas
Date: Thu Feb 25 2016 - 09:42:29 EST
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