> -----Original Message----- > From: Michael S. Tsirkin [mailto:mst@xxxxxxxxxx] > Sent: Tuesday, December 11, 2018 10:19 AM > To: linux-kernel@xxxxxxxxxxxxxxx > Cc: xuyandong <xuyandong2@xxxxxxxxxx>; stable@xxxxxxxxxxxxxxx; Yinghai > Lu <yinghai@xxxxxxxxxx>; Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>; Bjorn > Helgaas <bhelgaas@xxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx > Subject: [PATCH] pci: avoid bridge feature re-probing on hotplug > > commit 1f82de10d6 ("PCI/x86: don't assume prefetchable ranges are > 64bit") added probing of bridge support for 64 bit memory each time bridge is > re-enumerated. > > Unfortunately this probing is destructive if any device behind the bridge is in > use at this time. > > There's no real need to re-probe the bridge features as the regiters in question > never change - detect that using the memory flag being set and skip the > probing. > Avoiding repeated calls to pci_bridge_check_ranges might be even nicer would > be a bigger patch and probably not appropriate on stable. > > Reported-by: xuyandong <xuyandong2@xxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Cc: Yinghai Lu <yinghai@xxxxxxxxxx> > Cc: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> Tested-by: xuyandong <xuyandong2@xxxxxxxxxx> > --- > > This issue has been reported on upstream Linux and Centos. > > drivers/pci/setup-bus.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c index > ed960436df5e..7ab42f76579e 100644 > --- a/drivers/pci/setup-bus.c > +++ b/drivers/pci/setup-bus.c > @@ -741,6 +741,13 @@ static void pci_bridge_check_ranges(struct pci_bus > *bus) > struct resource *b_res; > > b_res = &bridge->resource[PCI_BRIDGE_RESOURCES]; > + > + /* Don't re-check after this was called once already: > + * important since bridge might be in use. > + */ > + if (b_res[1].flags & IORESOURCE_MEM) > + return; > + > b_res[1].flags |= IORESOURCE_MEM; > > pci_read_config_word(bridge, PCI_IO_BASE, &io); > -- > MST
