From: Marcel Apfelbaum <marcel.a@redhat.com>
To: Ronen Hod <rhod@redhat.com>
Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
bhelgaas@google.com, mst@redhat.com
Subject: Re: [PATCH] PCI/shpchp: fix a bus speed issue on hotplug
Date: Sun, 04 May 2014 17:07:26 +0300 [thread overview]
Message-ID: <1399212446.4302.13.camel@localhost.localdomain> (raw)
In-Reply-To: <5366451E.1050800@redhat.com>
On Sun, 2014-05-04 at 16:48 +0300, Ronen Hod wrote:
> On 05/01/2014 05:35 PM, Marcel Apfelbaum wrote:
> > When a board is added, the shpchp driver checks if there
> > is a mismatch between the bridge's adapter and the bus speed.
> > If there is, it sets the subordinate speed (if there is no device on it).
>
> Since the speed is irrelevant when running in a VM, I suggest that
> you either ignore it altogether, or "normalize" the speed of all the
> devices/bridges/buses in QEMU in order to avoid any conflicts
> in the first place.
Before this patch, this would not help since the primary bus speed
is not even set by the kernel.
After this patch, normalizing the QEMU device/bus/... speed may help
avoiding future conflicts, but we should discuss it in qemu mailing list :).
Ignoring emulated/para-virt device's speed when running in a VM it is\
a good question, but I don't know if such a distinction would be feasible.
Any thoughts would be appreciated,
Thanks,
Marcel
>
> Thanks, Ronen.
>
> >
> > However, it takes the reference of the board speed from the primary bus
> > and not from the subordinate. If the primary bus is PCI and not PCIX/PCIe,
> > its speed is not updated and remains 0xff. As a result hotplug fails
> > with error: "Speed of bus ff and adapter 0 mismatch".
> >
> > Fixed that by checking the speed against the subordinate bus.
> >
> > Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> > Acked-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> > drivers/pci/hotplug/shpchp_ctrl.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/hotplug/shpchp_ctrl.c b/drivers/pci/hotplug/shpchp_ctrl.c
> > index 5849927..6efc2ec 100644
> > --- a/drivers/pci/hotplug/shpchp_ctrl.c
> > +++ b/drivers/pci/hotplug/shpchp_ctrl.c
> > @@ -282,8 +282,8 @@ static int board_added(struct slot *p_slot)
> > return WRONG_BUS_FREQUENCY;
> > }
> >
> > - bsp = ctrl->pci_dev->bus->cur_bus_speed;
> > - msp = ctrl->pci_dev->bus->max_bus_speed;
> > + bsp = ctrl->pci_dev->subordinate->cur_bus_speed;
> > + msp = ctrl->pci_dev->subordinate->max_bus_speed;
> >
> > /* Check if there are other slots or devices on the same bus */
> > if (!list_empty(&ctrl->pci_dev->subordinate->devices))
>
next prev parent reply other threads:[~2014-05-04 14:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-01 14:35 [PATCH] PCI/shpchp: fix a bus speed issue on hotplug Marcel Apfelbaum
2014-05-01 15:43 ` Michael S. Tsirkin
2014-05-01 18:02 ` Bjorn Helgaas
2014-05-01 18:13 ` Marcel Apfelbaum
2014-05-01 18:57 ` Marcel Apfelbaum
2014-05-01 20:00 ` Bjorn Helgaas
2014-05-01 20:36 ` Marcel Apfelbaum
2014-05-04 10:40 ` Marcel Apfelbaum
2014-05-04 13:48 ` Ronen Hod
2014-05-04 14:07 ` Marcel Apfelbaum [this message]
2014-05-15 18:41 ` Bjorn Helgaas
2014-05-17 18:47 ` Michael S. Tsirkin
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