Re: [KERNEL PATCH v9 3/3] xen/privcmd: Add new syscall to get gsi from dev

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

On 2024/9/21 05:17, Stefano Stabellini wrote:
> On Fri, 20 Sep 2024, Chen, Jiqian wrote:
>> On 2024/9/19 06:49, Stefano Stabellini wrote:
>>> On Thu, 12 Sep 2024, Jiqian Chen wrote:
>>>> On PVH dom0, when passthrough a device to domU, QEMU and xl tools
>>>> want to use gsi number to do pirq mapping, see QEMU code
>>>> xen_pt_realize->xc_physdev_map_pirq, and xl code
>>>> pci_add_dm_done->xc_physdev_map_pirq, but in current codes, the gsi
>>>> number is got from file /sys/bus/pci/devices/<sbdf>/irq, that is
>>>> wrong, because irq is not equal with gsi, they are in different
>>>> spaces, so pirq mapping fails.
>>>> And in current linux codes, there is no method to get gsi
>>>> for userspace.
>>>>
>>>> For above purpose, record gsi of pcistub devices when init
>>>> pcistub and add a new syscall into privcmd to let userspace
>>>> can get gsi when they have a need.
>>>>
>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
>>>> Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
>>>> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
>>>> ---
>>>> v8->v9 changes:
>>>> Changed the syscall name from "IOCTL_PRIVCMD_GSI_FROM_DEV" to 
>>>> "IOCTL_PRIVCMD_PCIDEV_GET_GSI". Also changed the other functions name.
>>>> Changed the macro wrapping "pcistub_get_gsi_from_sbdf" from 
>>>> "CONFIG_XEN_ACPI" to "CONFIG_XEN_PCIDEV_BACKEND" to fix compile errors 
>>>> reported by CI robot.
>>>> Changed the parameter gsi of struct privcmd_pcidev_get_gsi from int to u32.
>>>>
>>>> v7->v8 changes:
>>>> In function privcmd_ioctl_gsi_from_dev, return -EINVAL when not confige 
>>>> CONFIG_XEN_ACPI.
>>>> Used PCI_BUS_NUM PCI_SLOT PCI_FUNC instead of open coding.
>>>>
>>>> v6->v7 changes:
>>>> Changed implementation to add a new parameter "gsi" to struct 
>>>> pcistub_device and set gsi when pcistub initialize device. Then when 
>>>> userspace wants to get gsi and pass sbdf, we can return that gsi.
>>>>
>>>> v5->v6 changes:
>>>> Changed implementation to add a new syscall to translate irq to gsi, 
>>>> instead adding a new gsi sysfs node, because the pci Maintainer didn't 
>>>> allow to add that sysfs node.
>>>>
>>>> v3->v5 changes:
>>>> No.
>>>>
>>>> v2->v3 changes:
>>>> Suggested by Roger: Abandoned previous implementations that added new 
>>>> syscall to get gsi from irq and changed to add a new sysfs node for gsi, 
>>>> then userspace can get gsi number from sysfs node.
>>>> ---
>>>> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
>>>> | Closes: 
>>>> https://lore.kernel.org/oe-kbuild-all/202406090826.whl6Cb7R-lkp@xxxxxxxxx/
>>>> ---
>>>> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
>>>> | Closes: 
>>>> https://lore.kernel.org/oe-kbuild-all/202405171113.T431PC8O-lkp@xxxxxxxxx/
>>>> ---
>>>>  drivers/xen/privcmd.c              | 30 +++++++++++++++++++++++
>>>>  drivers/xen/xen-pciback/pci_stub.c | 38 +++++++++++++++++++++++++++---
>>>>  include/uapi/xen/privcmd.h         |  7 ++++++
>>>>  include/xen/acpi.h                 |  9 +++++++
>>>>  4 files changed, 81 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
>>>> index 9563650dfbaf..1ed612d21543 100644
>>>> --- a/drivers/xen/privcmd.c
>>>> +++ b/drivers/xen/privcmd.c
>>>> @@ -46,6 +46,9 @@
>>>>  #include <xen/page.h>
>>>>  #include <xen/xen-ops.h>
>>>>  #include <xen/balloon.h>
>>>> +#ifdef CONFIG_XEN_ACPI
>>>> +#include <xen/acpi.h>
>>>> +#endif
>>>>  
>>>>  #include "privcmd.h"
>>>>  
>>>> @@ -844,6 +847,29 @@ static long privcmd_ioctl_mmap_resource(struct file 
>>>> *file,
>>>>    return rc;
>>>>  }
>>>>  
>>>> +static long privcmd_ioctl_pcidev_get_gsi(struct file *file, void __user 
>>>> *udata)
>>>> +{
>>>> +#ifdef CONFIG_XEN_ACPI
>>>> +  int rc;
>>>> +  struct privcmd_pcidev_get_gsi kdata;
>>>> +
>>>> +  if (copy_from_user(&kdata, udata, sizeof(kdata)))
>>>> +          return -EFAULT;
>>>> +
>>>> +  rc = pcistub_get_gsi_from_sbdf(kdata.sbdf);
>>>> +  if (rc < 0)
>>>> +          return rc;
>>>> +
>>>> +  kdata.gsi = rc;
>>>> +  if (copy_to_user(udata, &kdata, sizeof(kdata)))
>>>> +          return -EFAULT;
>>>> +
>>>> +  return 0;
>>>> +#else
>>>> +  return -EINVAL;
>>>> +#endif
>>>> +}
>>>> +
>>>>  #ifdef CONFIG_XEN_PRIVCMD_EVENTFD
>>>>  /* Irqfd support */
>>>>  static struct workqueue_struct *irqfd_cleanup_wq;
>>>> @@ -1543,6 +1569,10 @@ static long privcmd_ioctl(struct file *file,
>>>>            ret = privcmd_ioctl_ioeventfd(file, udata);
>>>>            break;
>>>>  
>>>> +  case IOCTL_PRIVCMD_PCIDEV_GET_GSI:
>>>> +          ret = privcmd_ioctl_pcidev_get_gsi(file, udata);
>>>> +          break;
>>>> +
>>>>    default:
>>>>            break;
>>>>    }
>>>> diff --git a/drivers/xen/xen-pciback/pci_stub.c 
>>>> b/drivers/xen/xen-pciback/pci_stub.c
>>>> index 8ce27333f54b..2ea8e4075adc 100644
>>>> --- a/drivers/xen/xen-pciback/pci_stub.c
>>>> +++ b/drivers/xen/xen-pciback/pci_stub.c
>>>> @@ -56,6 +56,9 @@ struct pcistub_device {
>>>>  
>>>>    struct pci_dev *dev;
>>>>    struct xen_pcibk_device *pdev;/* non-NULL if struct pci_dev is in use */
>>>> +#ifdef CONFIG_XEN_ACPI
>>>> +  int gsi;
>>>> +#endif
>>>>  };
>>>>  
>>>>  /* Access to pcistub_devices & seized_devices lists and the 
>>>> initialize_devices
>>>> @@ -88,6 +91,9 @@ static struct pcistub_device 
>>>> *pcistub_device_alloc(struct pci_dev *dev)
>>>>  
>>>>    kref_init(&psdev->kref);
>>>>    spin_lock_init(&psdev->lock);
>>>> +#ifdef CONFIG_XEN_ACPI
>>>> +  psdev->gsi = -1;
>>>> +#endif
>>>>  
>>>>    return psdev;
>>>>  }
>>>> @@ -220,6 +226,25 @@ static struct pci_dev 
>>>> *pcistub_device_get_pci_dev(struct xen_pcibk_device *pdev,
>>>>    return pci_dev;
>>>>  }
>>>>  
>>>> +#ifdef CONFIG_XEN_PCIDEV_BACKEND
>>>
>>>
>>> This breaks configurations without CONFIG_ACPI and with
>>> CONFIG_XEN_PCIDEV_BACKEND.
>>>
>>> Also there should be no dependency between PCIDEV_BACKEND and
>>> pcistub_get_gsi_from_sbdf.
>>>
>>> I think we should solve the build issues this way:
>>>
>>> - privcmd_ioctl_pcidev_get_gsi should have:
>>> #if defined(CONFIG_XEN_ACPI) && defined(CONFIG_XEN_PCI_STUB)
>>>
>>> - here we should have #ifdef CONFIG_XEN_ACPI as you had before
>>>
>>>
>>> As far as I can tell the above should be able to address all valid
>>> combinations.
>> This can't pass a combination that:
>> CONFIG_XEN_ACPI=y
>> CONFIG_XEN_PCI_STUB=y
>> CONFIG_XEN_PCIDEV_BACKEND=m
>> Reported by robot 
>> https://lore.kernel.org/oe-kbuild-all/202406090826.whl6Cb7R-lkp@xxxxxxxxx/
>>
>> At this combination, privcmd_ioctl_pcidev_get_gsi can call 
>> pcistub_get_gsi_from_sbdf because CONFIG_XEN_ACPI and CONFIG_XEN_PCI_STUB 
>> are both "y".
>> But when the compiler tries to find the implementation of 
>> pcistub_get_gsi_from_sbdf, it fails (ld: vmlinux.o: in function 
>> `privcmd_ioctl_pcidev_get_gsi':
>> /home/cjq/code/upstream/kernel_test_robot/linux_xen/build_dir/../drivers/xen/privcmd.c:859:
>>  undefined reference to `pcistub_get_gsi_from_sbdf'), because the value of 
>> CONFIG_XEN_PCIDEV_BACKEND is "m" (file drivers/xen/xen-pciback/Makefile 
>> shows "obj-$(CONFIG_XEN_PCIDEV_BACKEND) += xen-pciback.o"), so that 
>> xen-pciback is built as a module.
> 
> 
> The attached .config, with the appended changes on top of your patch
> work for me. I have CONFIG_XEN_PCIDEV_BACKEND=m.
Using your attached .config, it also works for me.
The difference between your .config and the config reported by Robot 
(https://download.01.org/0day-ci/archive/20240609/202406090826.whl6Cb7R-lkp@xxxxxxxxx/config)
 is that your CONFIG_XEN_PRIVCMD=m, but Robot's CONFIG_XEN_PRIVCMD=y.

It seems that, with my patch changes, privcmd uses the function implemented by 
xen-pciback, so if the configuration is "CONFIG_XEN_PRIVCMD=m & 
CONFIG_XEN_PCIDEV_BACKEND=m" or "CONFIG_XEN_PRIVCMD=y & 
CONFIG_XEN_PCIDEV_BACKEND=y", the compilation is OK, but if the configuration 
is "CONFIG_XEN_PRIVCMD=y & CONFIG_XEN_PCIDEV_BACKEND=m", issue happens.

You can change CONFIG_XEN_PRIVCMD from "m" to "y" in your .config, then you 
will fail at:
ld: vmlinux.o: in function `privcmd_ioctl':
privcmd.c:(.text+0x665e42): undefined reference to `pcistub_get_gsi_from_sbdf'

> 
> 
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 1ed612d21543..49e1c5e0c32a 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -849,7 +849,7 @@ static long privcmd_ioctl_mmap_resource(struct file *file,
>  
>  static long privcmd_ioctl_pcidev_get_gsi(struct file *file, void __user 
> *udata)
>  {
> -#ifdef CONFIG_XEN_ACPI
> +#if defined(CONFIG_XEN_ACPI) && defined(CONFIG_XEN_PCI_STUB)
>       int rc;
>       struct privcmd_pcidev_get_gsi kdata;
>  
> diff --git a/drivers/xen/xen-pciback/pci_stub.c 
> b/drivers/xen/xen-pciback/pci_stub.c
> index 2ea8e4075adc..d5807b622a59 100644
> --- a/drivers/xen/xen-pciback/pci_stub.c
> +++ b/drivers/xen/xen-pciback/pci_stub.c
> @@ -226,7 +226,7 @@ static struct pci_dev *pcistub_device_get_pci_dev(struct 
> xen_pcibk_device *pdev,
>       return pci_dev;
>  }
>  
> -#ifdef CONFIG_XEN_PCIDEV_BACKEND
> +#ifdef CONFIG_ACPI
>  int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
>  {
>       struct pcistub_device *psdev;

-- 
Best regards,
Jiqian Chen.