xen/privcmd: Add new syscall to get gsi from dev

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@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Message-ID: <20240924061437.2636766-4-Jiqian.Chen@amd.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/Kconfig

@@ -261,6 +261,7 @@ config XEN_SCSI_BACKEND
 config XEN_PRIVCMD
 	tristate "Xen hypercall passthrough driver"
 	depends on XEN
+	imply CONFIG_XEN_PCIDEV_BACKEND
 	default m
 	help
 	  The hypercall passthrough driver allows privileged user programs to

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 +847,31 @@ static long privcmd_ioctl_mmap_resource(struct file *file,
 	return rc;
 }
 
+static long privcmd_ioctl_pcidev_get_gsi(struct file *file, void __user *udata)
+{
+#if defined(CONFIG_XEN_ACPI)
+	int rc = -EINVAL;
+	struct privcmd_pcidev_get_gsi kdata;
+
+	if (copy_from_user(&kdata, udata, sizeof(kdata)))
+		return -EFAULT;
+
+	if (IS_REACHABLE(CONFIG_XEN_PCIDEV_BACKEND))
+		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 +1571,10 @@ 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;
 	}

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_ACPI
+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);
 

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__ */

include/xen/acpi.h

@@ -91,4 +91,13 @@ static inline int xen_acpi_get_gsi_info(struct pci_dev *dev,
 }
 #endif
 
+#ifdef CONFIG_XEN_PCI_STUB
+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 */