[PATCH v2] xen: Remove dependency between pciback and privcmd

[Jiqian Chen <Jiqian.Chen@amd.com>]

Commit 2fae6bb7be32 ("xen/privcmd: Add new syscall to get gsi from dev")
adds a weak reverse dependency to the config XEN_PRIVCMD definition, that
dependency causes xen-privcmd can't be loaded on domU, because
dependent xen-pciback is always not be loaded successfully on domU.

To solve above problem, remove that dependency, and do not call
pcistub_get_gsi_from_sbdf() directly, instead add a hook in
drivers/xen/apci.c, xen-pciback register the real call function, then in
privcmd_ioctl_pcidev_get_gsi call that hook.

Fixes: 2fae6bb7be32 ("xen/privcmd: Add new syscall to get gsi from dev")
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>
---
v1->v2 changes:
Added hook xen_acpi_get_gsi_from_sbdf.
Changed pcistub_get_gsi_from_sbdf to static and pciback register it as the real hook function.
---
 drivers/xen/Kconfig                |  1 -
 drivers/xen/acpi.c                 | 17 +++++++++++++++++
 drivers/xen/privcmd.c              |  6 ++----
 drivers/xen/xen-pciback/pci_stub.c |  4 ++--
 include/xen/acpi.h                 | 12 ++++--------
 5 files changed, 25 insertions(+), 15 deletions(-)

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 72ddee4c1544..f7d6f47971fd 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -261,7 +261,6 @@ config XEN_SCSI_BACKEND
 config XEN_PRIVCMD
 	tristate "Xen hypercall passthrough driver"
 	depends on XEN
-	imply XEN_PCIDEV_BACKEND
 	default m
 	help
 	  The hypercall passthrough driver allows privileged user programs to
diff --git a/drivers/xen/acpi.c b/drivers/xen/acpi.c
index 9e2096524fbc..0bff2f3a87d2 100644
--- a/drivers/xen/acpi.c
+++ b/drivers/xen/acpi.c
@@ -125,3 +125,20 @@ int xen_acpi_get_gsi_info(struct pci_dev *dev,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(xen_acpi_get_gsi_info);
+
+get_gsi_from_sbdf_t get_gsi_from_sbdf = NULL;
+
+void xen_acpi_register_get_gsi_func(get_gsi_from_sbdf_t func)
+{
+	get_gsi_from_sbdf = func;
+}
+EXPORT_SYMBOL_GPL(xen_acpi_register_get_gsi_func);
+
+int xen_acpi_get_gsi_from_sbdf(u32 sbdf)
+{
+	if (get_gsi_from_sbdf)
+		return get_gsi_from_sbdf(sbdf);
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(xen_acpi_get_gsi_from_sbdf);
\ No newline at end of file
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 3273cb8c2a66..4f75bc876454 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -850,15 +850,13 @@ static long privcmd_ioctl_mmap_resource(struct file *file,
 static long privcmd_ioctl_pcidev_get_gsi(struct file *file, void __user *udata)
 {
 #if defined(CONFIG_XEN_ACPI)
-	int rc = -EINVAL;
+	int rc;
 	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);
-
+	rc = xen_acpi_get_gsi_from_sbdf(kdata.sbdf);
 	if (rc < 0)
 		return rc;
 
diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index 2f3da5ac62cd..900e6199eec7 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -227,7 +227,7 @@ static struct pci_dev *pcistub_device_get_pci_dev(struct xen_pcibk_device *pdev,
 }
 
 #ifdef CONFIG_XEN_ACPI
-int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
+static int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
 {
 	struct pcistub_device *psdev;
 	int domain = (sbdf >> 16) & 0xffff;
@@ -242,7 +242,6 @@ int pcistub_get_gsi_from_sbdf(unsigned int sbdf)
 
 	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,
@@ -484,6 +483,7 @@ static int pcistub_init_device(struct pcistub_device *psdev)
 		if (err)
 			goto config_release;
 		psdev->gsi = gsi;
+		xen_acpi_register_get_gsi_func(pcistub_get_gsi_from_sbdf);
 	}
 #endif
 
diff --git a/include/xen/acpi.h b/include/xen/acpi.h
index daa96a22d257..ef4f70e4a557 100644
--- a/include/xen/acpi.h
+++ b/include/xen/acpi.h
@@ -91,13 +91,9 @@ 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
+typedef int (*get_gsi_from_sbdf_t)(u32 sbdf);
+
+void xen_acpi_register_get_gsi_func(get_gsi_from_sbdf_t func);
+int xen_acpi_get_gsi_from_sbdf(unsigned int sbdf);
 
 #endif	/* _XEN_ACPI_H */
-- 
2.34.1