Re: [RFC XEN PATCH v2 1/3] xen/vpci: Clear all vpci status of device

["Chen, Jiqian" <Jiqian.Chen@xxxxxxx>]

Hi Roger and Daniel P. Smith,

On 2023/11/28 22:08, Roger Pau Monné wrote:
> On Fri, Nov 24, 2023 at 06:41:34PM +0800, 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 all out of date compare with the real device state.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, this patch add new hypercall to clear
>> all vpci device state. And when reset device happens on dom0
>> side, dom0 can call this hypercall to notify vpci.
>>
>> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
>> Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
>> ---
>>  xen/arch/x86/hvm/hypercall.c  |  1 +
>>  xen/drivers/passthrough/pci.c | 21 +++++++++++++++++++++
>>  xen/drivers/pci/physdev.c     | 14 ++++++++++++++
>>  xen/drivers/vpci/vpci.c       |  9 +++++++++
>>  xen/include/public/physdev.h  |  2 ++
>>  xen/include/xen/pci.h         |  1 +
>>  xen/include/xen/vpci.h        |  6 ++++++
>>  7 files changed, 54 insertions(+)
>>
>> diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
>> index eeb73e1aa5..6ad5b4d5f1 100644
>> --- a/xen/arch/x86/hvm/hypercall.c
>> +++ b/xen/arch/x86/hvm/hypercall.c
>> @@ -84,6 +84,7 @@ long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
>> arg)
>>      case PHYSDEVOP_pci_mmcfg_reserved:
>>      case PHYSDEVOP_pci_device_add:
>>      case PHYSDEVOP_pci_device_remove:
>> +    case PHYSDEVOP_pci_device_state_reset:
>>      case PHYSDEVOP_dbgp_op:
>>          if ( !is_hardware_domain(currd) )
>>              return -ENOSYS;
>> diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
>> index 04d00c7c37..f871715585 100644
>> --- a/xen/drivers/passthrough/pci.c
>> +++ b/xen/drivers/passthrough/pci.c
>> @@ -824,6 +824,27 @@ int pci_remove_device(u16 seg, u8 bus, u8 devfn)
>>      return ret;
>>  }
>>  
>> +int pci_reset_device_state(u16 seg, u8 bus, u8 devfn)
> 
> You could use pci_sbdf_t here instead of 3 parameters.
Will change in next version, thank you.

> 
> I'm however unsure whether we really need this helper just to fetch
> the pdev and call vpci_reset_device_state(), I think you could place
> this logic directly in pci_physdev_op().  Unless there are plans to
> use such logic outside of pci_physdev_op().
If I place the logic of pci_reset_device_state directly in pci_physdev_op. I 
think I need to declare vpci_reset_device_state in pci.h? If it is suitable, I 
will change in next version.

> 
>> +{
>> +    struct pci_dev *pdev;
>> +    int ret = -ENODEV;
> 
> Some XSM check should be introduced fro this operation, as none of the
> existing ones is suitable.  See xsm_resource_unplug_pci() for example.
> 
> xsm_resource_reset_state_pci() or some such I would assume.
I don't know what I should do in XSM function(assume it is 
xsm_resource_reset_state_pci).
Hi Daniel P. Smith, could you please give me some suggestions?
Just to check the XSM_PRIV action?

> 
> (adding the XSM maintainer for feedback).
> 
>> +
>> +    pcidevs_lock();
>> +
>> +    pdev = pci_get_pdev(NULL, PCI_SBDF(seg, bus, devfn));
>> +    if ( !pdev )
>> +        goto error;
>> +
>> +    ret = vpci_reset_device_state(pdev);
>> +    if (ret)
>> +        printk(XENLOG_ERR "PCI reset device %pp state failed\n", 
>> &pdev->sbdf);
>> +
>> +error:
>> +    pcidevs_unlock();
>> +
>> +    return ret;
>> +}
>> +
>>  /* Caller should hold the pcidevs_lock */
>>  static int deassign_device(struct domain *d, uint16_t seg, uint8_t bus,
>>                             uint8_t devfn)
>> diff --git a/xen/drivers/pci/physdev.c b/xen/drivers/pci/physdev.c
>> index 42db3e6d13..cfdb545654 100644
>> --- a/xen/drivers/pci/physdev.c
>> +++ b/xen/drivers/pci/physdev.c
>> @@ -67,6 +67,20 @@ ret_t pci_physdev_op(int cmd, 
>> XEN_GUEST_HANDLE_PARAM(void) arg)
>>          break;
>>      }
>>  
>> +    case PHYSDEVOP_pci_device_state_reset: {
>> +        struct physdev_pci_device dev;
>> +
>> +        if ( !is_pci_passthrough_enabled() )
>> +            return -EOPNOTSUPP;
>> +
>> +        ret = -EFAULT;
>> +        if ( copy_from_guest(&dev, arg, 1) != 0 )
>> +            break;
>> +
>> +        ret = pci_reset_device_state(dev.seg, dev.bus, dev.devfn);
>> +        break;
>> +    }
>> +
>>      default:
>>          ret = -ENOSYS;
>>          break;
>> diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
>> index 3bec9a4153..e9c3eb1cd6 100644
>> --- a/xen/drivers/vpci/vpci.c
>> +++ b/xen/drivers/vpci/vpci.c
>> @@ -103,6 +103,15 @@ int vpci_add_handlers(struct pci_dev *pdev)
>>  
>>      return rc;
>>  }
>> +
>> +int vpci_reset_device_state(struct pci_dev *pdev)
>> +{
>> +    ASSERT(pcidevs_locked());
>> +
>> +    vpci_remove_device(pdev);
>> +    return vpci_add_handlers(pdev);
>> +}
>> +
>>  #endif /* __XEN__ */
>>  
>>  static int vpci_register_cmp(const struct vpci_register *r1,
>> diff --git a/xen/include/public/physdev.h b/xen/include/public/physdev.h
>> index f0c0d4727c..4156948903 100644
>> --- a/xen/include/public/physdev.h
>> +++ b/xen/include/public/physdev.h
>> @@ -305,6 +305,8 @@ struct physdev_pci_device {
>>  typedef struct physdev_pci_device physdev_pci_device_t;
>>  DEFINE_XEN_GUEST_HANDLE(physdev_pci_device_t);
>>  
>> +#define PHYSDEVOP_pci_device_state_reset      32
> 
> This needs some comment in order to explain the expected behaviour,
> and might be better placed a bit up after PHYSDEVOP_release_msix.
I will add some comment and move it closer to PHYSDEVOP_release_msix in next 
version. Thank you.

> 
> Thanks, Roger.

-- 
Best regards,
Jiqian Chen.