Re: [RFC KERNEL PATCH v4 1/3] xen/pci: Add xen_reset_device_state function

[Stefano Stabellini]

On Fri, 5 Jan 2024, Jiqian Chen wrote:
> When device on dom0 side has been reset, the vpci on Xen side
> won't get notification, so that the cached state in vpci is
> all out of date with the real device state.
> To solve that problem, add a new function to clear all vpci
> device state when device is reset on dom0 side.
> 
> And call that function in pcistub_init_device. Because when
> using "pci-assignable-add" to assign a passthrough device in
> Xen, it will reset passthrough device and the vpci state will
> out of date, and then device will fail to restore bar state.
> 
> Co-developed-by: Huang Rui <ray.huang@xxxxxxx>
> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  drivers/xen/pci.c                  | 12 ++++++++++++
>  drivers/xen/xen-pciback/pci_stub.c | 18 +++++++++++++++---
>  include/xen/interface/physdev.h    |  7 +++++++
>  include/xen/pci.h                  |  6 ++++++
>  4 files changed, 40 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
> index 72d4e3f193af..e9b30bc09139 100644
> --- a/drivers/xen/pci.c
> +++ b/drivers/xen/pci.c
> @@ -177,6 +177,18 @@ static int xen_remove_device(struct device *dev)
>  	return r;
>  }
>  
> +int xen_reset_device_state(const struct pci_dev *dev)
> +{
> +	struct physdev_pci_device device = {
> +		.seg = pci_domain_nr(dev->bus),
> +		.bus = dev->bus->number,
> +		.devfn = dev->devfn
> +	};
> +
> +	return HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_state_reset, &device);
> +}
> +EXPORT_SYMBOL_GPL(xen_reset_device_state);
> +
>  static int xen_pci_notifier(struct notifier_block *nb,
>  			    unsigned long action, void *data)
>  {
> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> index e34b623e4b41..46c40ec8a18e 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -89,6 +89,16 @@ static struct pcistub_device *pcistub_device_alloc(struct pci_dev *dev)
>  	return psdev;
>  }
>  
> +static int pcistub_reset_device_state(struct pci_dev *dev)
> +{
> +	__pci_reset_function_locked(dev);
> +
> +	if (!xen_pv_domain())
> +		return xen_reset_device_state(dev);
> +	else
> +		return 0;
> +}
> +
>  /* Don't call this directly as it's called by pcistub_device_put */
>  static void pcistub_device_release(struct kref *kref)
>  {
> @@ -107,7 +117,7 @@ static void pcistub_device_release(struct kref *kref)
>  	/* Call the reset function which does not take lock as this
>  	 * is called from "unbind" which takes a device_lock mutex.
>  	 */
> -	__pci_reset_function_locked(dev);
> +	pcistub_reset_device_state(dev);
>  	if (dev_data &&
>  	    pci_load_and_free_saved_state(dev, &dev_data->pci_saved_state))
>  		dev_info(&dev->dev, "Could not reload PCI state\n");
> @@ -284,7 +294,7 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
>  	 * (so it's ready for the next domain)
>  	 */
>  	device_lock_assert(&dev->dev);
> -	__pci_reset_function_locked(dev);
> +	pcistub_reset_device_state(dev);
>  
>  	dev_data = pci_get_drvdata(dev);
>  	ret = pci_load_saved_state(dev, dev_data->pci_saved_state);
> @@ -420,7 +430,9 @@ static int pcistub_init_device(struct pci_dev *dev)
>  		dev_err(&dev->dev, "Could not store PCI conf saved state!\n");
>  	else {
>  		dev_dbg(&dev->dev, "resetting (FLR, D3, etc) the device\n");
> -		__pci_reset_function_locked(dev);
> +		err = pcistub_reset_device_state(dev);
> +		if (err)
> +			goto config_release;
>  		pci_restore_state(dev);
>  	}
>  	/* Now disable the device (this also ensures some private device
> diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
> index a237af867873..8609770e28f5 100644
> --- a/include/xen/interface/physdev.h
> +++ b/include/xen/interface/physdev.h
> @@ -256,6 +256,13 @@ struct physdev_pci_device_add {
>   */
>  #define PHYSDEVOP_prepare_msix          30
>  #define PHYSDEVOP_release_msix          31
> +/*
> + * Notify the hypervisor that a PCI device has been reset, so that any
> + * internally cached state is regenerated.  Should be called after any
> + * device reset performed by the hardware domain.
> + */
> +#define PHYSDEVOP_pci_device_state_reset     32
> +
>  struct physdev_pci_device {
>      /* IN */
>      uint16_t seg;
> diff --git a/include/xen/pci.h b/include/xen/pci.h
> index b8337cf85fd1..b2e2e856efd6 100644
> --- a/include/xen/pci.h
> +++ b/include/xen/pci.h
> @@ -4,10 +4,16 @@
>  #define __XEN_PCI_H__
>  
>  #if defined(CONFIG_XEN_DOM0)
> +int xen_reset_device_state(const struct pci_dev *dev);
>  int xen_find_device_domain_owner(struct pci_dev *dev);
>  int xen_register_device_domain_owner(struct pci_dev *dev, uint16_t domain);
>  int xen_unregister_device_domain_owner(struct pci_dev *dev);
>  #else
> +static inline int xen_reset_device_state(const struct pci_dev *dev)
> +{
> +	return -1;
> +}
> +
>  static inline int xen_find_device_domain_owner(struct pci_dev *dev)
>  {
>  	return -1;
> -- 
> 2.34.1
>