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Message-ID: <20160623125955.647008cb@t450s.home>
Date: Thu, 23 Jun 2016 12:59:55 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Sinan Kaya <okaya@...eaurora.org>
Cc: kvm@...r.kernel.org, timur@...eaurora.org, cov@...eaurora.org,
jcm@...hat.com, eric.auger@...hat.com, linux-acpi@...r.kernel.org,
agross@...eaurora.org, linux-arm-msm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Baptiste Reynal <b.reynal@...tualopensystems.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 7/9] vfio, platform: make reset driver a requirement
by default
On Mon, 20 Jun 2016 11:51:17 -0400
Sinan Kaya <okaya@...eaurora.org> wrote:
> The code was allowing platform devices to be used without a supporting
> VFIO reset driver. The hardware can be left in some inconsistent state
> after a guest machine abort.
>
> The reset driver will put the hardware back to safe state and disable
> interrupts before returning the control back to the host machine.
>
> Adding a new reset_required kernel module option to AMBA and platform
> VFIO drivers with a default value of true.
>
> New requirements are:
> 1. A reset function needs to be implemented by the corresponding driver
> via DT/ACPI.
> 2. The reset function needs to be discovered via DT/ACPI.
>
> The probe of the driver will fail if any of the above conditions are
> not satisfied.
>
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
> drivers/vfio/platform/vfio_amba.c | 5 +++++
> drivers/vfio/platform/vfio_platform.c | 5 +++++
> drivers/vfio/platform/vfio_platform_common.c | 24 ++++++++++++++++--------
> drivers/vfio/platform/vfio_platform_private.h | 1 +
> 4 files changed, 27 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/vfio/platform/vfio_amba.c b/drivers/vfio/platform/vfio_amba.c
> index a66479b..7585902 100644
> --- a/drivers/vfio/platform/vfio_amba.c
> +++ b/drivers/vfio/platform/vfio_amba.c
> @@ -23,6 +23,10 @@
> #define DRIVER_AUTHOR "Antonios Motakis <a.motakis@...tualopensystems.com>"
> #define DRIVER_DESC "VFIO for AMBA devices - User Level meta-driver"
>
> +static bool reset_required = true;
> +module_param(reset_required, bool, 0644);
> +MODULE_PARM_DESC(reset_required, "override reset requirement (default: 1)");
> +
> /* probing devices from the AMBA bus */
>
> static struct resource *get_amba_resource(struct vfio_platform_device *vdev,
> @@ -68,6 +72,7 @@ static int vfio_amba_probe(struct amba_device *adev, const struct amba_id *id)
> vdev->get_resource = get_amba_resource;
> vdev->get_irq = get_amba_irq;
> vdev->parent_module = THIS_MODULE;
> + vdev->reset_required = reset_required;
>
> ret = vfio_platform_probe_common(vdev, &adev->dev);
> if (ret) {
> diff --git a/drivers/vfio/platform/vfio_platform.c b/drivers/vfio/platform/vfio_platform.c
> index b1cc3a7..ef89146 100644
> --- a/drivers/vfio/platform/vfio_platform.c
> +++ b/drivers/vfio/platform/vfio_platform.c
> @@ -23,6 +23,10 @@
> #define DRIVER_AUTHOR "Antonios Motakis <a.motakis@...tualopensystems.com>"
> #define DRIVER_DESC "VFIO for platform devices - User Level meta-driver"
>
> +static bool reset_required = true;
> +module_param(reset_required, bool, 0644);
> +MODULE_PARM_DESC(reset_required, "override reset requirement (default: 1)");
> +
> /* probing devices from the linux platform bus */
>
> static struct resource *get_platform_resource(struct vfio_platform_device *vdev,
> @@ -66,6 +70,7 @@ static int vfio_platform_probe(struct platform_device *pdev)
> vdev->get_resource = get_platform_resource;
> vdev->get_irq = get_platform_irq;
> vdev->parent_module = THIS_MODULE;
> + vdev->reset_required = reset_required;
Do you see value in making the global reset_required changeable, with
the behavior of any given device dependent on the setting of this
variable at the time of probe? It seems like a bit of a support issue
to me. Also, we're breaking existing users if there are any with this
change. Should we introduce a CONFIG option to set the default? I
think we can get away with changing the default that way, but I'm not
so sure otherwise.
>
> ret = vfio_platform_probe_common(vdev, &pdev->dev);
> if (ret)
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index 1d771a6..b9ffed4 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -128,10 +128,10 @@ static bool vfio_platform_has_reset(struct vfio_platform_device *vdev)
> return vdev->of_reset ? true : false;
> }
>
> -static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
> +static int vfio_platform_get_reset(struct vfio_platform_device *vdev)
> {
> if (vdev->acpihid)
> - return;
> + return vfio_platform_acpi_has_reset(vdev) ? 0 : -ENOENT;
>
> vdev->of_reset = vfio_platform_lookup_reset(vdev->compat,
> &vdev->reset_module);
> @@ -140,6 +140,8 @@ static void vfio_platform_get_reset(struct vfio_platform_device *vdev)
> vdev->of_reset = vfio_platform_lookup_reset(vdev->compat,
> &vdev->reset_module);
> }
> +
> + return vdev->of_reset ? 0 : -ENOENT;
> }
nit, this looks more like a:
static bool vfio_platform_has_reset(...)
...
return vfio_platform_acpi_has_reset() == 0;
...
return vdev->of_reset != NULL
>
> static void vfio_platform_put_reset(struct vfio_platform_device *vdev)
> @@ -663,6 +665,13 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
>
> vdev->device = dev;
>
> + ret = vfio_platform_get_reset(vdev);
> + if (ret && vdev->reset_required) {
> + pr_err("vfio: no reset function found for device %s\n",
> + vdev->name);
> + return ret;
> + }
> +
> group = iommu_group_get(dev);
> if (!group) {
> pr_err("VFIO: No IOMMU group for device %s\n", vdev->name);
> @@ -670,16 +679,15 @@ int vfio_platform_probe_common(struct vfio_platform_device *vdev,
> }
>
> ret = vfio_add_group_dev(dev, &vfio_platform_ops, vdev);
> - if (ret) {
> - iommu_group_put(group);
> - return ret;
> - }
> -
> - vfio_platform_get_reset(vdev);
> + if (ret)
> + goto out;
>
> mutex_init(&vdev->igate);
>
> return 0;
> +out:
> + iommu_group_put(group);
> + return ret;
> }
> EXPORT_SYMBOL_GPL(vfio_platform_probe_common);
>
> diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
> index ba9e4f8..68fbc00 100644
> --- a/drivers/vfio/platform/vfio_platform_private.h
> +++ b/drivers/vfio/platform/vfio_platform_private.h
> @@ -50,6 +50,7 @@ struct vfio_platform_region {
> };
>
> struct vfio_platform_device {
> + bool reset_required;
> struct vfio_platform_region *regions;
> u32 num_regions;
> struct vfio_platform_irq *irqs;
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