linux-kernel - Re: [PATCH v8 17/22] vfio-pci/zdev: add open/close device hooks

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Message-ID: <20220524210815.GB1343366@nvidia.com>
Date:   Tue, 24 May 2022 18:08:15 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>
Cc:     linux-s390@...r.kernel.org, alex.williamson@...hat.com,
        cohuck@...hat.com, schnelle@...ux.ibm.com, farman@...ux.ibm.com,
        pmorel@...ux.ibm.com, borntraeger@...ux.ibm.com, hca@...ux.ibm.com,
        gor@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        agordeev@...ux.ibm.com, svens@...ux.ibm.com, frankja@...ux.ibm.com,
        david@...hat.com, imbrenda@...ux.ibm.com, vneethv@...ux.ibm.com,
        oberpar@...ux.ibm.com, freude@...ux.ibm.com, thuth@...hat.com,
        pasic@...ux.ibm.com, pbonzini@...hat.com, corbet@....net,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH v8 17/22] vfio-pci/zdev: add open/close device hooks

On Tue, May 24, 2022 at 02:59:02PM -0400, Matthew Rosato wrote:
> During vfio-pci open_device, pass the KVM associated with the vfio group
> (if one exists).  This is needed in order to pass a special indicator
> (GISA) to firmware to allow zPCI interpretation facilities to be used
> for only the specific KVM associated with the vfio-pci device.  During
> vfio-pci close_device, unregister the notifier.
> 
> Signed-off-by: Matthew Rosato <mjrosato@...ux.ibm.com>
>  arch/s390/include/asm/pci.h      |  2 ++
>  drivers/vfio/pci/vfio_pci_core.c | 11 ++++++++++-
>  drivers/vfio/pci/vfio_pci_zdev.c | 27 +++++++++++++++++++++++++++
>  include/linux/vfio_pci_core.h    | 12 ++++++++++++
>  4 files changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 85eb0ef9d4c3..67fbce1ea0c9 100644
> +++ b/arch/s390/include/asm/pci.h
> @@ -5,6 +5,7 @@
>  #include <linux/pci.h>
>  #include <linux/mutex.h>
>  #include <linux/iommu.h>
> +#include <linux/notifier.h>
>  #include <linux/pci_hotplug.h>
>  #include <asm-generic/pci.h>
>  #include <asm/pci_clp.h>
> @@ -195,6 +196,7 @@ struct zpci_dev {
>  	struct s390_domain *s390_domain; /* s390 IOMMU domain data */
>  	struct kvm_zdev *kzdev;
>  	struct mutex kzdev_lock;
> +	struct notifier_block nb; /* vfio notifications */

This is obsolete now right? Same for the #include ?

> @@ -418,6 +424,9 @@ void vfio_pci_core_disable(struct vfio_pci_core_device *vdev)
>  
>  	vdev->needs_reset = true;
>  
> +	if (vfio_pci_zdev_release(vdev))
> +		pci_info(pdev, "%s: Couldn't restore zPCI state\n", __func__);
> +
>  	/*
>  	 * If we have saved state, restore it.  If we can reset the device,
>  	 * even better.  Resetting with current state seems better than
> diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
> index ea4c0d2b0663..d0df85c8b204 100644
> +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> @@ -11,6 +11,7 @@
>  #include <linux/uaccess.h>
>  #include <linux/vfio.h>
>  #include <linux/vfio_zdev.h>
> +#include <linux/kvm_host.h>
>  #include <asm/pci_clp.h>
>  #include <asm/pci_io.h>
>  
> @@ -136,3 +137,29 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
>  
>  	return ret;
>  }
> +
> +int vfio_pci_zdev_open(struct vfio_pci_core_device *vdev)
> +{
> +	struct zpci_dev *zdev = to_zpci(vdev->pdev);
> +
> +	if (!zdev)
> +		return -ENODEV;
> +
> +	if (!vdev->vdev.kvm)
> +		return 0;
> +
> +	return kvm_s390_pci_register_kvm(zdev, vdev->vdev.kvm);
> +}
> +
> +int vfio_pci_zdev_release(struct vfio_pci_core_device *vdev)
> +{
> +	struct zpci_dev *zdev = to_zpci(vdev->pdev);

Keeping these functions named open_device/close_device wouuld probably
be clearer

> +	if (!zdev)
> +		return -ENODEV;
> +
> +	if (!vdev->vdev.kvm)
> +		return 0;
> +
> +	return kvm_s390_pci_unregister_kvm(zdev);
> +}

Again this cannot fail, you should make it return void, not ignore the
failure - or at least push the ignoring the failure down to the place
that is causing this.

Otherwise it looks fine to me, thanks

Jason