Re: [KERNEL PATCH v9 1/3] xen/pci: Add a function to reset device for xen

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 12 Sep 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 all out of date with the real device state.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 out of date, and then device will fail to restore bar state.
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
> Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>


Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>



> ---
> v8->v9 changes:
> Due to the struct and name of the hypercall changed on Xen side, I did the 
> corresponding changes, so removed the Reviewed-by of Stefano. But no function 
> changes actually.
> 
> v5->v8 changes:
> No.
> 
> v4->v5 changes:
> Added Reviewed-by of Stefano.
> 
> v3->v4 changes:
> Changed the code comment of PHYSDEVOP_pci_device_state_reset.
> Used a new function pcistub_reset_device_state to wrap 
> __pci_reset_function_locked and xen_reset_device_state, and called 
> pcistub_reset_device_state in pci_stub.c.
> 
> v2->v3 changes:
> Added condition to limit do xen_reset_device_state for no-pv domain in 
> pcistub_init_device.
> 
> v1->v2 changes:
> New patch to add a new function to call reset hypercall.
> ---
>  drivers/xen/pci.c                  | 13 +++++++++++++
>  drivers/xen/xen-pciback/pci_stub.c | 18 +++++++++++++++---
>  include/xen/interface/physdev.h    | 17 +++++++++++++++++
>  include/xen/pci.h                  |  6 ++++++
>  4 files changed, 51 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c
> index 72d4e3f193af..bb59524b8bbd 100644
> --- a/drivers/xen/pci.c
> +++ b/drivers/xen/pci.c
> @@ -177,6 +177,19 @@ static int xen_remove_device(struct device *dev)
>       return r;
>  }
>  
> +int xen_reset_device(const struct pci_dev *dev)
> +{
> +     struct pci_device_reset device = {
> +             .dev.seg = pci_domain_nr(dev->bus),
> +             .dev.bus = dev->bus->number,
> +             .dev.devfn = dev->devfn,
> +             .flags = PCI_DEVICE_RESET_FLR,
> +     };
> +
> +     return HYPERVISOR_physdev_op(PHYSDEVOP_pci_device_reset, &device);
> +}
> +EXPORT_SYMBOL_GPL(xen_reset_device);
> +
>  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 4faebbb84999..3e162c1753e2 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(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..df74e65a884b 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_reset      32
> +
>  struct physdev_pci_device {
>      /* IN */
>      uint16_t seg;
> @@ -263,6 +270,16 @@ struct physdev_pci_device {
>      uint8_t devfn;
>  };
>  
> +struct pci_device_reset {
> +    struct physdev_pci_device dev;
> +#define PCI_DEVICE_RESET_COLD 0x0
> +#define PCI_DEVICE_RESET_WARM 0x1
> +#define PCI_DEVICE_RESET_HOT  0x2
> +#define PCI_DEVICE_RESET_FLR  0x3
> +#define PCI_DEVICE_RESET_MASK 0x3
> +    uint32_t flags;
> +};
> +
>  #define PHYSDEVOP_DBGP_RESET_PREPARE    1
>  #define PHYSDEVOP_DBGP_RESET_DONE       2
>  
> diff --git a/include/xen/pci.h b/include/xen/pci.h
> index b8337cf85fd1..424b8ea89ca8 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(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(const struct pci_dev *dev)
> +{
> +     return -1;
> +}
> +
>  static inline int xen_find_device_domain_owner(struct pci_dev *dev)
>  {
>       return -1;
> -- 
> 2.34.1
>