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SubjectRe: linux-next: manual merge of the vhost tree with the pci tree
On Wed, Jan 30, 2019 at 8:40 PM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> Hi all,
>
> Today's linux-next merge of the vhost tree got a conflict in:
>
> drivers/pci/setup-bus.c
>
> between commit:
>
> 51c48b310183 ("PCI: Probe bridge window attributes once at enumeration-time")
>
> from the pci tree and commit:
>
> 955156f34e7d ("PCI: avoid bridge feature re-probing on hotplug")
>
> from the vhost tree.
>
> I fixed it up (hopefully - see below) and can carry the fix as
> necessary. This is now fixed as far as linux-next is concerned, but any
> non trivial conflicts should be mentioned to your upstream maintainer
> when your tree is submitted for merging. You may also want to consider
> cooperating with the maintainer of the conflicting tree to minimise any
> particularly complex conflicts.

51c48b310183 and 955156f34e7d are both to solve the same problem, so I
think the best resolution is to drop 955156f34e7d from the vhost tree
completely.

The remaining wrinkle to work out is that we need a stable backport.
51c48b310183 is technically a little large for a stable backport, so I
want to have a solid justification for it. As soon as I get a
kernel.org bugzilla with those details (who's affected by the
breakage, what the failure looks like, how to reproduce it, etc), I'll
add that URL and the stable tag.

Bjorn

> diff --cc drivers/pci/setup-bus.c
> index 1941bb0a6c13,d5c25d465d97..000000000000
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@@ -735,17 -735,50 +735,26 @@@ int pci_claim_bridge_resource(struct pc
> base/limit registers must be read-only and read as 0. */
> static void pci_bridge_check_ranges(struct pci_bus *bus)
> {
> - u16 io;
> - u32 pmem;
> struct pci_dev *bridge = bus->self;
> - struct resource *b_res;
> -
> - b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> + struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
>
> + /*
> + * Don't re-check after this was called once already:
> + * important since bridge might be in use.
> + * Note: this is only reliable because as per spec all PCI to PCI
> + * bridges support memory unconditionally so IORESOURCE_MEM is set.
> + */
> + if (b_res[1].flags & IORESOURCE_MEM)
> + return;
> +
> b_res[1].flags |= IORESOURCE_MEM;
>
> - pci_read_config_word(bridge, PCI_IO_BASE, &io);
> - if (!io) {
> - pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> - pci_read_config_word(bridge, PCI_IO_BASE, &io);
> - pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> - }
> - if (io)
> + if (bridge->io_window)
> b_res[0].flags |= IORESOURCE_IO;
>
> - /* DECchip 21050 pass 2 errata: the bridge may miss an address
> - disconnect boundary by one PCI data phase.
> - Workaround: do not use prefetching on this device. */
> - if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> - return;
> -
> - pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> - if (!pmem) {
> - pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> - 0xffe0fff0);
> - pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> - pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> - }
> - if (pmem) {
> + if (bridge->pref_window) {
> b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH;
> - if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> - PCI_PREF_RANGE_TYPE_64) {
> + if (bridge->pref_64_window) {
> b_res[2].flags |= IORESOURCE_MEM_64;
> b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
> }

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