RE: [PATCH v2 1/2] backends/iommufd.c: report error when /dev/iommu is not available

[Duan, Zhenzhong]

>-----Original Message-----
>From: Pierrick Bouvier <pierrick.bouv...@linaro.org>
>Subject: [PATCH v2 1/2] backends/iommufd.c: report error when /dev/iommu is
>not available
>
>In case current kernel does not support /dev/iommu, qemu will probably
>fail first because /sys/bus/pci/devices/*/vfio-dev/ is not present,
>since QEMU opens it before /dev/iommu.
>
>Instead, report an error directly when completing an iommufd object, to
>inform user that kernel does not support it, with a hint about missing
>CONFIG_IOMMUFD. We can't do this from initialize as there is no way to
>return an error, and we don't want to abort at this step.
>
>Reviewed-by: Philippe Mathieu-Daudé <phi...@linaro.org>
>Signed-off-by: Pierrick Bouvier <pierrick.bouv...@linaro.org>
>---
> backends/iommufd.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
>diff --git a/backends/iommufd.c b/backends/iommufd.c
>index acfab907c03..2c3ca23ca0f 100644
>--- a/backends/iommufd.c
>+++ b/backends/iommufd.c
>@@ -72,6 +72,12 @@ static bool
>iommufd_backend_can_be_deleted(UserCreatable *uc)
>
> static void iommufd_backend_complete(UserCreatable *uc, Error **errp)
> {
>+    if (!g_file_test("/dev/iommu", G_FILE_TEST_EXISTS)) {
>+        error_setg(errp, "/dev/iommu does not exist"
>+                         " (is your kernel config missing CONFIG_IOMMUFD?)");
>+        return;
>+    }
>+
>     IOMMUFDBackend *be = IOMMUFD_BACKEND(uc);
>     const char *name = iommufd_fd_name(be);

I think more accurately it could be:

@@ -82,7 +82,12 @@ static void iommufd_backend_complete(UserCreatable *uc, 
Error **errp)
         } else {
             cpr_save_fd(name, 0, be->fd);
         }
+    } else if (!g_file_test("/dev/iommu", G_FILE_TEST_EXISTS)) {
+        error_setg(errp, "/dev/iommu does not exist"
+                         " (is your kernel config missing CONFIG_IOMMUFD?)");
+        return;
     }
+
 }

Thanks
Zhenzhong