Re: [XEN PATCH v11 1/8] xen/vpci: Clear all vpci status of device

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.06.2024 14:33, Jiqian Chen wrote:
> When a device has been reset on dom0 side, the vpci on Xen
> side won't get notification, so the cached state in vpci is
> all out of date compare with the real device state.
> To solve that problem, add a new hypercall to clear all vpci
> device state. When the state of device is reset on dom0 side,
> dom0 can call this hypercall to notify vpci.

While the description properly talks about all of this being about device
reset, the title suggests otherwise (leaving open what the context is, thus
- to me at least - suggesting it's during vPCI init for a particular
device).

> @@ -67,6 +68,63 @@ ret_t pci_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
> arg)
>          break;
>      }
>  
> +    case PHYSDEVOP_pci_device_state_reset:
> +    {
> +        struct pci_device_state_reset dev_reset;
> +        struct pci_dev *pdev;
> +        pci_sbdf_t sbdf;
> +
> +        ret = -EOPNOTSUPP;
> +        if ( !is_pci_passthrough_enabled() )
> +            break;
> +
> +        ret = -EFAULT;
> +        if ( copy_from_guest(&dev_reset, arg, 1) != 0 )
> +            break;
> +
> +        sbdf = PCI_SBDF(dev_reset.dev.seg,
> +                        dev_reset.dev.bus,
> +                        dev_reset.dev.devfn);
> +
> +        ret = xsm_resource_setup_pci(XSM_PRIV, sbdf.sbdf);
> +        if ( ret )
> +            break;
> +
> +        pcidevs_lock();
> +        pdev = pci_get_pdev(NULL, sbdf);
> +        if ( !pdev )
> +        {
> +            pcidevs_unlock();
> +            ret = -ENODEV;
> +            break;
> +        }
> +
> +        write_lock(&pdev->domain->pci_lock);
> +        pcidevs_unlock();
> +        /* Implement FLR, other reset types may be implemented in future */

The comment isn't in sync with the code anymore.

> +        switch ( dev_reset.reset_type )
> +        {
> +        case PCI_DEVICE_STATE_RESET_COLD:
> +        case PCI_DEVICE_STATE_RESET_WARM:
> +        case PCI_DEVICE_STATE_RESET_HOT:
> +        case PCI_DEVICE_STATE_RESET_FLR:
> +        {

This brace isn't needed while at the same time it is confusing.

> +            ret = vpci_reset_device_state(pdev, dev_reset.reset_type);
> +            if ( ret )
> +                dprintk(XENLOG_ERR,
> +                        "%pp: failed to reset vPCI device state\n", &sbdf);

I question the need for a log message here.

> --- a/xen/include/public/physdev.h
> +++ b/xen/include/public/physdev.h
> @@ -296,6 +296,13 @@ DEFINE_XEN_GUEST_HANDLE(physdev_pci_device_add_t);
>   */
>  #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;
> @@ -305,6 +312,19 @@ struct physdev_pci_device {
>  typedef struct physdev_pci_device physdev_pci_device_t;
>  DEFINE_XEN_GUEST_HANDLE(physdev_pci_device_t);
>  
> +struct pci_device_state_reset {
> +    physdev_pci_device_t dev;
> +#define _PCI_DEVICE_STATE_RESET_COLD 0
> +#define PCI_DEVICE_STATE_RESET_COLD  (1U<<_PCI_DEVICE_STATE_RESET_COLD)
> +#define _PCI_DEVICE_STATE_RESET_WARM 1
> +#define PCI_DEVICE_STATE_RESET_WARM  (1U<<_PCI_DEVICE_STATE_RESET_WARM)
> +#define _PCI_DEVICE_STATE_RESET_HOT  2
> +#define PCI_DEVICE_STATE_RESET_HOT   (1U<<_PCI_DEVICE_STATE_RESET_HOT)
> +#define _PCI_DEVICE_STATE_RESET_FLR  3
> +#define PCI_DEVICE_STATE_RESET_FLR   (1U<<_PCI_DEVICE_STATE_RESET_FLR)
> +    uint32_t reset_type;
> +};

Do we really need the _PCI_DEVICE_STATE_RESET_* bit positions as separate
#define-s? I can't spot any use anywhere.

Jan