From 5dde383e2ef5e22fe7db689dc38c1aabfb801449 Mon Sep 17 00:00:00 2001 From: Bjorn Helgaas Date: Mon, 9 Jul 2012 13:38:41 -0600 Subject: [PATCH] PCI: allow P2P bridge windows starting at PCI bus address zero cd81e1ea1a4c added checks that prevent us from using P2P bridge windows that start at PCI bus address zero. The reason was to "prevent us from overwriting resources that are unassigned." But generic code should allow address zero in both BARs and bridge windows, so I think that commit was a mistake. Windows at bus address zero are legal and likely to exist on machines with an offset between bus addresses and CPU addresses. For example, in the following hypothetical scenario, the bridge at 00:01.0 has a window at bus address zero and the device at 01:00.0 has a BAR at bus address zero, and I think both are perfectly valid: PCI host bridge to bus 0000:00 pci_bus 0000:00: root bus resource [mem 0x100000000-0x1ffffffff] (bus address [0x00000000-0xffffffff]) pci 0000:00:01.0: PCI bridge to [bus 01] pci 0000:00:01.0: bridge window [mem 0x100000000-0x100ffffff] pci 0000:01:00.0: reg 10: [mem 0x100000000-0x100ffffff] Acked-by: Yinghai Lu Signed-off-by: Bjorn Helgaas --- drivers/pci/probe.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 658ac977cb56..9c5d2a992999 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -287,7 +287,7 @@ static void __devinit pci_read_bridge_io(struct pci_bus *child) limit |= (io_limit_hi << 16); } - if (base && base <= limit) { + if (base <= limit) { res->flags = (io_base_lo & PCI_IO_RANGE_TYPE_MASK) | IORESOURCE_IO; res2.flags = res->flags; region.start = base; @@ -314,7 +314,7 @@ static void __devinit pci_read_bridge_mmio(struct pci_bus *child) pci_read_config_word(dev, PCI_MEMORY_LIMIT, &mem_limit_lo); base = (mem_base_lo & PCI_MEMORY_RANGE_MASK) << 16; limit = (mem_limit_lo & PCI_MEMORY_RANGE_MASK) << 16; - if (base && base <= limit) { + if (base <= limit) { res->flags = (mem_base_lo & PCI_MEMORY_RANGE_TYPE_MASK) | IORESOURCE_MEM; region.start = base; region.end = limit + 0xfffff; @@ -360,7 +360,7 @@ static void __devinit pci_read_bridge_mmio_pref(struct pci_bus *child) #endif } } - if (base && base <= limit) { + if (base <= limit) { res->flags = (mem_base_lo & PCI_PREF_RANGE_TYPE_MASK) | IORESOURCE_MEM | IORESOURCE_PREFETCH; if (res->flags & PCI_PREF_RANGE_TYPE_64) -- GitLab