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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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.



> +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
>