[PATCH v4 3/7] PCI: Separate VF BAR updates from standard BAR updates

[Bjorn Helgaas]

On Thu, Dec 01, 2016 at 10:02:54AM +1100, Gavin Shan wrote:
> On Tue, Nov 29, 2016 at 06:06:05PM -0600, Bjorn Helgaas wrote:
> >On Wed, Nov 30, 2016 at 10:20:28AM +1100, Gavin Shan wrote:
> >> On Tue, Nov 29, 2016 at 08:48:26AM -0600, Bjorn Helgaas wrote:
> >> >On Tue, Nov 29, 2016 at 03:55:46PM +1100, Gavin Shan wrote:
> >> >> On Mon, Nov 28, 2016 at 10:15:06PM -0600, Bjorn Helgaas wrote:
> >> >> >Previously pci_update_resource() used the same code path for updating
> >> >> >standard BARs and VF BARs in SR-IOV capabilities.
> >> >> >
> >> >> >Split the VF BAR update into a new pci_iov_update_resource() internal
> >> >> >interface, which makes it simpler to compute the BAR address (we can get
> >> >> >rid of pci_resource_bar() and pci_iov_resource_bar()).
> >> >> >
> >> >> >This patch:
> >> >> >
> >> >> >  - Renames pci_update_resource() to pci_std_update_resource(),
> >> >> >  - Adds pci_iov_update_resource(),
> >> >> >  - Makes pci_update_resource() a wrapper that calls the appropriate one,
> >> >> >
> >> >> >No functional change intended.
> >
> >> >However, I don't think this code in pci_update_resource() is obviously
> >> >correct:
> >> >
> >> >  new = region.start | (res->flags & PCI_REGION_FLAG_MASK);
> >> >
> >> >PCI_REGION_FLAG_MASK is 0xf.  For memory BARs, bits 0-3 are read-only
> >> >property bits.  For I/O BARs, bits 0-1 are read-only and bits 2-3 are
> >> >part of the address, so on the face of it, the above could corrupt two
> >> >bits of an I/O address.
> >> >
> >> >It's true that decode_bar() initializes flags correctly, using
> >> >PCI_BASE_ADDRESS_IO_MASK for I/O BARs and PCI_BASE_ADDRESS_MEM_MASK
> >> >for memory BARs, but it would take a little more digging to be sure
> >> >that we never set bits 2-3 of flags for an I/O resource elsewhere.
> >> >
> >> 
> >> The BAR's property bits are probed from device-tree, not hardware
> >> on some platforms (e.g. pSeries). Also, there is only one (property)
> >> bit if it's a ROM BAR. So more check as below might be needed because
> >> the code (without the enhancement) should also work fine.
> >
> >Ah, right, I forgot about that.  I didn't do enough digging :)
> >
> >> >How about this in pci_std_update_resource():
> >> >
> >> >        pcibios_resource_to_bus(dev->bus, &region, res);
> >> >        new = region.start;
> >> >
> >> >        if (res->flags & IORESOURCE_IO) {
> >> >                mask = (u32)PCI_BASE_ADDRESS_IO_MASK;
> >> >                new |= res->flags & ~PCI_BASE_ADDRESS_IO_MASK;
> >> >        } else {
> >> >                mask = (u32)PCI_BASE_ADDRESS_MEM_MASK;
> >> >                new |= res->flags & ~PCI_BASE_ADDRESS_MEM_MASK;
> >> >        }
> >> >
> >> 
> >> 	if (res->flags & IORESOURCE_IO) {
> >> 		mask = (u32)PCI_BASE_ADDRESS_IO_MASK;
> >> 		new |= res->flags & ~PCI_BASE_ADDRESS_IO_MASK;
> >> 	} else if (resno < PCI_ROM_RESOURCE) {
> >> 		mask = (u32)PCI_BASE_ADDRESS_MEM_MASK;
> >> 		new |= res->flags & ~PCI_BASE_ADDRESS_MEM_MASK;
> >> 	} else if (resno == PCI_ROM_RESOURCE) {
> >> 		mask = ~((u32)IORESOURCE_ROM_ENABLE);
> >> 		new |= res->flags & IORESOURCE_ROM_ENABLE);
> >> 	} else {
> >> 		dev_warn(&dev->dev, "BAR#%d out of range\n", resno);
> >> 		return;
> >> 	}
> >
> >After this patch, the only thing we OR into a ROM BAR value is
> >PCI_ROM_ADDRESS_ENABLE, and that's done below, only if the ROM is
> >already enabled.
> >
> >I did update the ROM mask (to PCI_ROM_ADDRESS_MASK).  I'm not 100%
> >sure about doing that -- it follows the spec, but it is a change from
> >what we've been doing before.  I guess it should be safe because it
> >means we're checking fewer bits than before (only the top 21 bits for
> >ROMs, where we used check the top 28), so the only possible difference
> >is that we might not warn about "error updating" in some case where we
> >used to.
> >
> >I'm not really sure about the value of the "error updating" checks to
> >begin with, though I guess it does help us find broken devices that
> >put non-BARs where BARs are supposed to be.
> >
> 
> Yeah, agree. Bjorn, I don't have more comments. please take your time
> to respin the series and maybe applied it. I really want to see the
> fixes can be in 4.10 if possible :-)

These will definitely be in v4.10.  Thanks for all your help!