Hi Bjorn and Michael After trying to reproduce the problem for a whole day, the bug did not show up any more. So I think the new patch does solve this problem. > -----Original Message----- > From: Bjorn Helgaas [mailto:helgaas@xxxxxxxxxx] > Sent: Sunday, January 20, 2019 4:13 AM > To: Michael S. Tsirkin <mst@xxxxxxxxxx> > Cc: linux-kernel@xxxxxxxxxxxxxxx; xuyandong <xuyandong2@xxxxxxxxxx>; > Yinghai Lu <yinghai@xxxxxxxxxx>; Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>; > linux-pci@xxxxxxxxxxxxxxx; Sagi Grimberg <sagi@xxxxxxxxxxx>; Ofer Hayut > <ofer@xxxxxxxxxxxxxxxxx>; Roy Shterman <roys@xxxxxxxxxxxxxxxxx>; Keith > Busch <keith.busch@xxxxxxxxx>; Wangzhou (B) <wangzhou1@xxxxxxxxxxxxx> > Subject: [PATCH v3] PCI: avoid bridge feature re-probing on hotplug > > I gave up trying to reproduce the problem and test this patch with qemu; can > you guys (Michael and Xu (sorry if I mangled your name)) give this a try? > > I cc'd a few other people who have noticed this issue in the past, so just FYI for > them. > > Bjorn > > > commit dd21b922db366ba069291b6fef2a8ce6768756a2 > Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Date: Sat Jan 19 11:35:04 2019 -0600 > > PCI: Probe bridge window attributes once at enumeration-time > > pci_bridge_check_ranges() determines whether a bridge supports the > optional > I/O and prefetchable memory windows and sets the flag bits in the bridge > resources. This could be done once during enumeration except that the > resource allocation code completely clears the flag bits, e.g., in the > pci_assign_unassigned_bridge_resources() path. > > The problem was that in some cases pci_bridge_check_ranges() *changes* > the > window registers to determine whether they're writable, and this may break > concurrent accesses to devices behind the bridge. > > Add a new pci_read_bridge_windows() to determine whether a bridge > supports > the optional windows, call it once during enumeration, remember the > results, and change pci_bridge_check_ranges() to set the flag bits based on > those remembered results. > > Link: https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-email- > wangzhou1@xxxxxxxxxxxxx > Link: https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.html > Reported-by: xuyandong <xuyandong2@xxxxxxxxxx> > Cc: Sagi Grimberg <sagi@xxxxxxxxxxx> > Cc: Ofer Hayut <ofer@xxxxxxxxxxxxxxxxx> > Cc: Roy Shterman <roys@xxxxxxxxxxxxxxxxx> > Cc: Keith Busch <keith.busch@xxxxxxxxx> > Cc: Zhou Wang <wangzhou1@xxxxxxxxxxxxx> > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index > 257b9f6f2ebb..2ef8b954c65a 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev, > unsigned int howmany, int rom) > } > } > > +static void pci_read_bridge_windows(struct pci_dev *bridge) { > + u16 io; > + u32 pmem, tmp; > + > + 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) > + bridge->io_window = 1; > + > + /* > + * 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) > + return; > + > + bridge->pref_window = 1; > + > + if ((pmem & PCI_PREF_RANGE_TYPE_MASK) == > PCI_PREF_RANGE_TYPE_64) { > + > + /* > + * Bridge claims to have a 64-bit prefetchable memory > + * window; verify that the upper bits are actually > + * writable. > + */ > + pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, > &pmem); > + pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, > + 0xffffffff); > + pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, > &tmp); > + pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, > pmem); > + if (tmp) > + bridge->pref_64_window = 1; > + } > +} > + > static void pci_read_bridge_io(struct pci_bus *child) { > struct pci_dev *dev = child->self; > @@ -1739,6 +1790,7 @@ int pci_setup_device(struct pci_dev *dev) > pci_read_irq(dev); > dev->transparent = ((dev->class & 0xff) == 1); > pci_read_bases(dev, 2, PCI_ROM_ADDRESS1); > + pci_read_bridge_windows(dev); > set_pcie_hotplug_bridge(dev); > pos = pci_find_capability(dev, PCI_CAP_ID_SSVID); > if (pos) { > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c index > ed960436df5e..1941bb0a6c13 100644 > --- a/drivers/pci/setup-bus.c > +++ b/drivers/pci/setup-bus.c > @@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev > *bridge, int i) > 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; > + struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES]; > > - b_res = &bridge->resource[PCI_BRIDGE_RESOURCES]; > 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; > } > } > - > - /* double check if bridge does support 64 bit pref */ > - if (b_res[2].flags & IORESOURCE_MEM_64) { > - u32 mem_base_hi, tmp; > - pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, > - &mem_base_hi); > - pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, > - 0xffffffff); > - pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, > &tmp); > - if (!tmp) > - b_res[2].flags &= ~IORESOURCE_MEM_64; > - pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, > - mem_base_hi); > - } > } > > /* Helper function for sizing routines: find first available diff --git > a/include/linux/pci.h b/include/linux/pci.h index 65f1d8c2f082..40b327b814aa > 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -373,6 +373,9 @@ struct pci_dev { > bool match_driver; /* Skip attaching driver */ > > unsigned int transparent:1; /* Subtractive decode bridge > */ > + unsigned int io_window:1; /* Bridge has I/O window */ > + unsigned int pref_window:1; /* Bridge has pref mem > window */ > + unsigned int pref_64_window:1; /* Pref mem window is 64-bit > */ > unsigned int multifunction:1; /* Multi-function device */ > > unsigned int is_busmaster:1; /* Is busmaster */
