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

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

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.

> 
> 
> 
>> +int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
>> +{
>> +    struct pcistub_device *psdev;
>> +    int domain = (sbdf >> 16) & 0xffff;
>> +    int bus = PCI_BUS_NUM(sbdf);
>> +    int slot = PCI_SLOT(sbdf);
>> +    int func = PCI_FUNC(sbdf);
>> +
>> +    psdev = pcistub_device_find(domain, bus, slot, func);
>> +
>> +    if (!psdev)
>> +            return -ENODEV;
>> +
>> +    return psdev->gsi;
>> +}
>> +EXPORT_SYMBOL_GPL(pcistub_get_gsi_from_sbdf);
>> +#endif
>> +
>>  struct pci_dev *pcistub_get_pci_dev_by_slot(struct xen_pcibk_device *pdev,
>>                                          int domain, int bus,
>>                                          int slot, int func)
>> @@ -367,14 +392,20 @@ static int pcistub_match(struct pci_dev *dev)
>>      return found;
>>  }
>>  
>> -static int pcistub_init_device(struct pci_dev *dev)
>> +static int pcistub_init_device(struct pcistub_device *psdev)
>>  {
>>      struct xen_pcibk_dev_data *dev_data;
>> +    struct pci_dev *dev;
>>  #ifdef CONFIG_XEN_ACPI
>>      int gsi, trigger, polarity;
>>  #endif
>>      int err = 0;
>>  
>> +    if (!psdev)
>> +            return -EINVAL;
>> +
>> +    dev = psdev->dev;
>> +
>>      dev_dbg(&dev->dev, "initializing...\n");
>>  
>>      /* The PCI backend is not intended to be a module (or to work with
>> @@ -452,6 +483,7 @@ static int pcistub_init_device(struct pci_dev *dev)
>>              err = xen_pvh_setup_gsi(gsi, trigger, polarity);
>>              if (err)
>>                      goto config_release;
>> +            psdev->gsi = gsi;
>>      }
>>  #endif
>>  
>> @@ -494,7 +526,7 @@ static int __init pcistub_init_devices_late(void)
>>  
>>              spin_unlock_irqrestore(&pcistub_devices_lock, flags);
>>  
>> -            err = pcistub_init_device(psdev->dev);
>> +            err = pcistub_init_device(psdev);
>>              if (err) {
>>                      dev_err(&psdev->dev->dev,
>>                              "error %d initializing device\n", err);
>> @@ -564,7 +596,7 @@ static int pcistub_seize(struct pci_dev *dev,
>>              spin_unlock_irqrestore(&pcistub_devices_lock, flags);
>>  
>>              /* don't want irqs disabled when calling pcistub_init_device */
>> -            err = pcistub_init_device(psdev->dev);
>> +            err = pcistub_init_device(psdev);
>>  
>>              spin_lock_irqsave(&pcistub_devices_lock, flags);
>>  
>> diff --git a/include/uapi/xen/privcmd.h b/include/uapi/xen/privcmd.h
>> index 8b8c5d1420fe..8e2c8fd44764 100644
>> --- a/include/uapi/xen/privcmd.h
>> +++ b/include/uapi/xen/privcmd.h
>> @@ -126,6 +126,11 @@ struct privcmd_ioeventfd {
>>      __u8 pad[2];
>>  };
>>  
>> +struct privcmd_pcidev_get_gsi {
>> +    __u32 sbdf;
>> +    __u32 gsi;
>> +};
>> +
>>  /*
>>   * @cmd: IOCTL_PRIVCMD_HYPERCALL
>>   * @arg: &privcmd_hypercall_t
>> @@ -157,5 +162,7 @@ struct privcmd_ioeventfd {
>>      _IOW('P', 8, struct privcmd_irqfd)
>>  #define IOCTL_PRIVCMD_IOEVENTFD                                     \
>>      _IOW('P', 9, struct privcmd_ioeventfd)
>> +#define IOCTL_PRIVCMD_PCIDEV_GET_GSI                                \
>> +    _IOC(_IOC_NONE, 'P', 10, sizeof(struct privcmd_pcidev_get_gsi))
>>  
>>  #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
>> diff --git a/include/xen/acpi.h b/include/xen/acpi.h
>> index 3bcfe82d9078..393a73bfda24 100644
>> --- a/include/xen/acpi.h
>> +++ b/include/xen/acpi.h
>> @@ -91,4 +91,13 @@ static inline int xen_acpi_get_gsi_info(struct pci_dev 
>> *dev,
>>  }
>>  #endif
>>  
>> +#ifdef CONFIG_XEN_PCIDEV_BACKEND
>> +int pcistub_get_gsi_from_sbdf(unsigned int sbdf);
>> +#else
>> +static inline int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
>> +{
>> +    return -1;
>> +}
>> +#endif
>> +
>>  #endif      /* _XEN_ACPI_H */
>> -- 
>> 2.34.1
>>

-- 
Best regards,
Jiqian Chen.