[PATCH v8 7/8] vpci/msi: Free MSI resources when init_msi() fails

[Jiqian Chen <Jiqian.Chen@xxxxxxx>]

When init_msi() fails, current logic return fail and free MSI-related
resources in vpci_deassign_device(). But the previous new changes will
hide MSI capability and return success, it can't reach
vpci_deassign_device() to remove resources if hiding success, so those
resources must be removed in cleanup function of MSI.

To do that, implement cleanup function for MSI.

Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
---
cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
---
v7->v8 changes:
* Add a comment to describe why "-2" in cleanup_msi().
* Given the code in vpci_remove_registers() an error in the removal of
  registers would likely imply memory corruption, at which point it's
  best to fully disable the device. So, Rollback the last two modifications of 
v7.

v6->v7 changes:
* Change the pointer parameter of cleanup_msi() to be const.
* When vpci_remove_registers() in cleanup_msi() fails, not to return
  directly, instead try to free msi and re-add ctrl handler.
* Pass pdev->vpci into vpci_add_register() instead of pdev->vpci->msi in
  init_msi() since we need that every handler realize that msi is NULL
  when msi is free but handlers are still in there.

v5->v6 changes:
No.

v4->v5 changes:
* Change definition "static void cleanup_msi" to "static int cf_check 
cleanup_msi"
  since cleanup hook is changed to be int.
* Add a read-only register for MSI Control Register in the end of cleanup_msi.

v3->v4 changes:
* Change function name from fini_msi() to cleanup_msi().
* Remove unnecessary comment.
* Change to use XFREE to free vpci->msi.

v2->v3 changes:
* Remove all fail path, and use fini_msi() hook instead.
* Change the method to calculating the size of msi registers.

v1->v2 changes:
* Added a new function fini_msi to free all MSI resources instead of using an 
array
  to record registered registers.

Best regards,
Jiqian Chen.
---
 xen/drivers/vpci/msi.c | 46 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/vpci/msi.c b/xen/drivers/vpci/msi.c
index c3eba4e14870..ad5138c4cb5e 100644
--- a/xen/drivers/vpci/msi.c
+++ b/xen/drivers/vpci/msi.c
@@ -193,6 +193,50 @@ static void cf_check mask_write(
     msi->mask = val;
 }
 
+static int cf_check cleanup_msi(const struct pci_dev *pdev)
+{
+    int rc;
+    unsigned int end;
+    struct vpci *vpci = pdev->vpci;
+    const unsigned int msi_pos = pdev->msi_pos;
+    const unsigned int ctrl = msi_control_reg(msi_pos);
+
+    if ( !msi_pos || !vpci->msi )
+        return 0;
+
+    if ( vpci->msi->masking )
+        end = msi_pending_bits_reg(msi_pos, vpci->msi->address64);
+    else
+        /*
+         * "-2" here is to cut the reserved 2 bytes of Message Data when
+         * there is no masking support.
+         */
+        end = msi_mask_bits_reg(msi_pos, vpci->msi->address64) - 2;
+
+    rc = vpci_remove_registers(vpci, ctrl, end - ctrl);
+    if ( rc )
+    {
+        printk(XENLOG_ERR "%pd %pp: fail to remove MSI handlers rc=%d\n",
+               pdev->domain, &pdev->sbdf, rc);
+        ASSERT_UNREACHABLE();
+        return rc;
+    }
+
+    XFREE(vpci->msi);
+
+    /*
+     * The driver may not traverse the capability list and think device
+     * supports MSI by default. So here let the control register of MSI
+     * be Read-Only is to ensure MSI disabled.
+     */
+    rc = vpci_add_register(vpci, vpci_hw_read16, NULL, ctrl, 2, NULL);
+    if ( rc )
+        printk(XENLOG_ERR "%pd %pp: fail to add MSI ctrl handler rc=%d\n",
+               pdev->domain, &pdev->sbdf, rc);
+
+    return rc;
+}
+
 static int cf_check init_msi(struct pci_dev *pdev)
 {
     unsigned int pos = pdev->msi_pos;
@@ -270,7 +314,7 @@ static int cf_check init_msi(struct pci_dev *pdev)
 
     return 0;
 }
-REGISTER_VPCI_CAP(MSI, init_msi, NULL);
+REGISTER_VPCI_CAP(MSI, init_msi, cleanup_msi);
 
 void vpci_dump_msi(void)
 {
-- 
2.34.1