[Xen-devel] [PATCH for-4.5] call xc_domain_irq_permission before xc_domain_irq_permission

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

xc_physdev_unmap_pirq might revoke the permission to map the irq from
the domain causing the following xc_domain_irq_permission call to fail
and return error (domain_pirq_to_irq returns 0).

Call xc_domain_irq_permission first to prevent this from happening
(xc_physdev_unmap_pirq calls irq_deny_access, that doesn't fail if the
permission is already removed).

This is a simple bug fix and I think should go in 4.5.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

diff --git a/tools/libxl/libxl_pci.c b/tools/libxl/libxl_pci.c
index 316643c..904d255 100644
--- a/tools/libxl/libxl_pci.c
+++ b/tools/libxl/libxl_pci.c
@@ -1288,14 +1290,14 @@ skip1:
             goto out;
         }
         if ((fscanf(f, "%u", &irq) == 1) && irq) {
-            rc = xc_physdev_unmap_pirq(ctx->xch, domid, irq);
-            if (rc < 0) {
-                LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "xc_physdev_unmap_pirq 
irq=%d", irq);
-            }
             rc = xc_domain_irq_permission(ctx->xch, domid, irq, 0);
             if (rc < 0) {
                 LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, 
"xc_domain_irq_permission irq=%d", irq);
             }
+            rc = xc_physdev_unmap_pirq(ctx->xch, domid, irq);
+            if (rc < 0) {
+                LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "xc_physdev_unmap_pirq 
irq=%d", irq);
+            }
         }
         fclose(f);
     }

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