On Tue, Jun 02, 2015 at 02:37:31PM +0800, Jiang Liu wrote:
> Ccing Rafael, it's ACPI hotplug related.
>
> On 2015/6/2 14:36, Jiang Liu wrote:
> > The dmaengine core assumes that async DMA devices will only be removed
> > when they not used anymore, or it assumes dma_async_device_unregister()
> > will only be called by dma driver exit routines. But this assumption is
> > not true for the IOAT driver, which calls dma_async_device_unregister()
> > from ioat_remove(). So current IOAT driver doesn't support device
> > hot-removal because it may cause system crash to hot-remove an inuse
> > IOAT device.
> >
> > To support CPU socket hot-removal, all PCI devices, including IOAT
> > devices embedded in the socket, will be hot-removed. The idea solution
> > is to enhance the dmaengine core and IOAT driver to support hot-removal,
> > but that's too hard.
> >
> > This patch implements a hack to disable IOAT devices under hotplug-capable
> > CPU socket so it won't break socket hot-removal.
> >
So below looks okay though I wonder how hard would it be to fix hot unplug ?
--
~Vinod
> > Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxxxxxxx>
> > ---
> > drivers/dma/ioat/pci.c | 34 ++++++++++++++++++++++++++++++++++
> > 1 file changed, 34 insertions(+)
> >
> > diff --git a/drivers/dma/ioat/pci.c b/drivers/dma/ioat/pci.c
> > index 76f0dc688a19..3b8c9b03f4b3 100644
> > --- a/drivers/dma/ioat/pci.c
> > +++ b/drivers/dma/ioat/pci.c
> > @@ -27,6 +27,7 @@
> > #include <linux/interrupt.h>
> > #include <linux/dca.h>
> > #include <linux/slab.h>
> > +#include <linux/acpi.h>
> > #include "dma.h"
> > #include "dma_v2.h"
> > #include "registers.h"
> > @@ -148,6 +149,34 @@ alloc_ioatdma(struct pci_dev *pdev, void __iomem *iobase)
> > return d;
> > }
> >
> > +/*
> > + * The dmaengine core assumes that async DMA devices will only be removed
> > + * when they not used anymore, or it assumes dma_async_device_unregister()
> > + * will only be called by dma driver exit routines. But this assumption is
> > + * not true for the IOAT driver, which calls dma_async_device_unregister()
> > + * from ioat_remove(). So current IOAT driver doesn't support device
> > + * hot-removal because it may cause system crash to hot-remove inuse IOAT
> > + * devices.
> > + *
> > + * This is a hack to disable IOAT devices under ejectable PCI host bridge
> > + * so it won't break PCI host bridge hot-removal.
> > + */
> > +static bool ioat_pci_has_ejectable_acpi_ancestor(struct pci_dev *pdev)
> > +{
> > +#ifdef CONFIG_ACPI
> > + struct pci_bus *bus = pdev->bus;
> > + struct acpi_device *adev;
> > +
> > + while (bus->parent)
> > + bus = bus->parent;
> > + for (adev = ACPI_COMPANION(bus->bridge); adev; adev = adev->parent)
> > + if (adev->flags.ejectable)
> > + return true;
> > +#endif
> > +
> > + return false;
> > +}
> > +
> > static int ioat_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > {
> > void __iomem * const *iomap;
> > @@ -155,6 +184,11 @@ static int ioat_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> > struct ioatdma_device *device;
> > int err;
> >
> > + if (ioat_pci_has_ejectable_acpi_ancestor(pdev)) {
> > + dev_dbg(&pdev->dev, "ignore ejectable IOAT device.\n");
> > + return -ENODEV;
> > + }
> > +
> > err = pcim_enable_device(pdev);
> > if (err)
> > return err;
> >
--
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