On Tue, Dec 11, 2018 at 02:45:44AM +0000, xuyandong wrote: > > > > -----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> Bjorn could you queue this for this release? > > --- > > > > 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
