Re: [RFC KERNEL PATCH v7 2/2] xen/privcmd: Add new syscall to get gsi from dev

[Stefano Stabellini]

On Thu, 16 May 2024, Chen, Jiqian wrote:
> On 2024/5/16 06:42, Stefano Stabellini wrote:
> > On Wed, 15 May 2024, Jiqian Chen wrote:
> >> In PVH dom0, it uses the linux local interrupt mechanism,
> >> when it allocs irq for a gsi, it is dynamic, and follow
> >> the principle of applying first, distributing first. And
> >> the irq number is alloced from small to large, but the
> >> applying gsi number is not, may gsi 38 comes before gsi 28,
> >> it causes the irq number is not equal with the gsi number.
> >> And when passthrough a device, QEMU will use device's gsi
> >> number to do pirq mapping, but the gsi number is got from
> >> file /sys/bus/pci/devices/<sbdf>/irq, irq!= gsi, so it will
> >> fail when mapping.
> >> 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.
> >>
> >> Co-developed-by: Huang Rui <ray.huang@xxxxxxx>
> >> Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
> >> ---
> >>  drivers/xen/privcmd.c              | 28 ++++++++++++++++++++++
> >>  drivers/xen/xen-pciback/pci_stub.c | 38 +++++++++++++++++++++++++++---
> >>  include/uapi/xen/privcmd.h         |  7 ++++++
> >>  include/xen/acpi.h                 |  2 ++
> >>  4 files changed, 72 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> >> index 67dfa4778864..5953a03b5cb0 100644
> >> --- a/drivers/xen/privcmd.c
> >> +++ b/drivers/xen/privcmd.c
> >> @@ -45,6 +45,9 @@
> >>  #include <xen/page.h>
> >>  #include <xen/xen-ops.h>
> >>  #include <xen/balloon.h>
> >> +#ifdef CONFIG_ACPI
> >> +#include <xen/acpi.h>
> >> +#endif
> >>  
> >>  #include "privcmd.h"
> >>  
> >> @@ -842,6 +845,27 @@ static long privcmd_ioctl_mmap_resource(struct file *file,
> >>  	return rc;
> >>  }
> >>  
> >> +static long privcmd_ioctl_gsi_from_dev(struct file *file, void __user *udata)
> >> +{
> >> +	struct privcmd_gsi_from_dev kdata;
> >> +
> >> +	if (copy_from_user(&kdata, udata, sizeof(kdata)))
> >> +		return -EFAULT;
> >> +
> >> +#ifdef CONFIG_ACPI
> >> +	kdata.gsi = pcistub_get_gsi_from_sbdf(kdata.sbdf);
> >> +	if (kdata.gsi == -1)
> >> +		return -EINVAL;
> >> +#else
> >> +	kdata.gsi = -1;
> > 
> > Should we return an error instead, like -EINVAL, to make the behavior
> > more similar to the CONFIG_ACPI case?
> OK, will return -EINVAL if not config acpi.
> Like:
> static long privcmd_ioctl_gsi_from_dev(struct file *file, void __user *udata)
> {
> #ifdef CONFIG_ACPI
> 	struct privcmd_gsi_from_dev kdata;
> 
> 	if (copy_from_user(&kdata, udata, sizeof(kdata)))
> 		return -EFAULT;
> 
> 	kdata.gsi = pcistub_get_gsi_from_sbdf(kdata.sbdf);
> 	if (kdata.gsi == -1)
> 		return -EINVAL;
> 
> 	if (copy_to_user(udata, &kdata, sizeof(kdata)))
> 		return -EFAULT;
> 
> 	return 0;
> #else
> 	return -EINVAL;
> #endif
> }


Yep that's fine



> >> +#endif
> >> +
> >> +	if (copy_to_user(udata, &kdata, sizeof(kdata)))
> >> +		return -EFAULT;
> >> +
> >> +	return 0;
> >> +}
> >> +
> >>  #ifdef CONFIG_XEN_PRIVCMD_EVENTFD
> >>  /* Irqfd support */
> >>  static struct workqueue_struct *irqfd_cleanup_wq;
> >> @@ -1529,6 +1553,10 @@ static long privcmd_ioctl(struct file *file,
> >>  		ret = privcmd_ioctl_ioeventfd(file, udata);
> >>  		break;
> >>  
> >> +	case IOCTL_PRIVCMD_GSI_FROM_DEV:
> >> +		ret = privcmd_ioctl_gsi_from_dev(file, udata);
> >> +		break;
> >> +
> >>  	default:
> >>  		break;
> >>  	}
> >> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> >> index 2b90d832d0a7..4b62b4d377a9 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_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_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_ACPI
> >> +int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
> >> +{
> >> +	struct pcistub_device *psdev;
> >> +	int domain = sbdf >> 16;
> >> +	int bus = (sbdf >> 8) & 0xff;
> >> +	int slot = (sbdf >> 3) & 0x1f;
> >> +	int func = sbdf & 0x7;
> > 
> > you can use PCI_DEVFN PCI_SLOT PCI_FUNC pci_domain_nr instead of open
> > coding.
> Thanks, will change to use these in next version.
> But pci_domain_nr requires passing in pci_dev.
> Will change like:
> 	int domain = (sbdf >> 16) & 0xffff;
> 	int bus = PCI_BUS_NUM(sbdf);
> 	int slot = PCI_SLOT(sbdf);
> 	int func = PCI_FUNC(sbdf);

That's fine


 
> >> +
> >> +	psdev = pcistub_device_find(domain, bus, slot, func);
> >> +
> >> +	if (!psdev)
> >> +		return -1;
> >> +
> >> +	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_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
> >> @@ -448,6 +479,7 @@ static int pcistub_init_device(struct pci_dev *dev)
> >>  		dev_err(&dev->dev, "Fail to get gsi info!\n");
> >>  		goto config_release;
> >>  	}
> >> +	psdev->gsi = gsi;
> >>  
> >>  	if (xen_initial_domain() && xen_pvh_domain()) {
> >>  		err = xen_pvh_setup_gsi(gsi, trigger, polarity);
> >> @@ -495,7 +527,7 @@ 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);
> >> @@ -565,7 +597,7 @@ 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..220e7670a113 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_gsi_from_dev {
> >> +	__u32 sbdf;
> >> +	int 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_GSI_FROM_DEV				\
> >> +	_IOC(_IOC_NONE, 'P', 10, sizeof(struct privcmd_gsi_from_dev))
> >>  
> >>  #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
> >> diff --git a/include/xen/acpi.h b/include/xen/acpi.h
> >> index 9b50027113f3..0bf5f4884456 100644
> >> --- a/include/xen/acpi.h
> >> +++ b/include/xen/acpi.h
> >> @@ -83,4 +83,6 @@ int xen_acpi_get_gsi_info(struct pci_dev *dev,
> >>  						  int *gsi_out,
> >>  						  int *trigger_out,
> >>  						  int *polarity_out);
> >> +
> >> +int pcistub_get_gsi_from_sbdf(unsigned int sbdf);
> >>  #endif	/* _XEN_ACPI_H */
> >> -- 
> >> 2.34.1
> >>
> 
> -- 
> Best regards,
> Jiqian Chen.
>