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

[Jürgen Groß]

On 10.10.24 09:58, Jiqian Chen wrote:

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 <marma...@invisiblethingslab.com>
Signed-off-by: Jiqian Chen <jiqian.c...@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;

                return -EFAULT;

-               rc = pcistub_get_gsi_from_sbdf(kdata.sbdf);
-
+       rc = xen_acpi_get_gsi_from_sbdf(kdata.sbdf);
        if (rc < 0)
                return rc;

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,
  }

-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)

  }
-EXPORT_SYMBOL_GPL(pcistub_get_gsi_from_sbdf);
  #endif

@@ -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);

if (copy_from_user(&kdata, udata, sizeof(kdata))) - if (IS_REACHABLE(CONFIG_XEN_PCIDEV_BACKEND)) diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c #ifdef CONFIG_XEN_ACPI return psdev->gsi; struct pci_dev *pcistub_get_pci_dev_by_slot(struct xen_pcibk_device *pdev,

I don't think this is the right place for registering the function.

It should be done at the end of xen_pcibk_init() (guarded with CONFIG_XEN_ACPI).

Additionally you should reset the function pointer NULL in xen_pcibk_cleanup().


Juergen

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