-----Original Message----- From: Michael S. Tsirkin [mailto:mst@redhat.com] Sent: Tuesday, December 11, 2018 10:19 AM To: linux-kernel@vger.kernel.org Cc: xuyandong xuyandong2@huawei.com; stable@vger.kernel.org; Yinghai Lu yinghai@kernel.org; Jesse Barnes jbarnes@virtuousgeek.org; Bjorn Helgaas bhelgaas@google.com; linux-pci@vger.kernel.org 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@huawei.com Cc: stable@vger.kernel.org Cc: Yinghai Lu yinghai@kernel.org Cc: Jesse Barnes jbarnes@virtuousgeek.org Signed-off-by: Michael S. Tsirkin mst@redhat.com
Tested-by: xuyandong xuyandong2@huawei.com
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