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.
>
> 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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