Re: [PATCH V2 3/4] xen/unpopulated-alloc: Add mechanism to use Xen resource

From: Oleksandr
Date: Tue Nov 09 2021 - 13:52:01 EST



On 28.10.21 22:08, Boris Ostrovsky wrote:

Hi Boris

I am sorry for the late response.


On 10/26/21 12:05 PM, Oleksandr Tyshchenko wrote:
  +static void unpopulated_init(void)
+{
+    static bool inited = false;
+    int ret;
+
+    if (inited)
+        return;
+
+    /*
+     * Try to initialize Xen resource the first and fall back to default
+     * resource if arch doesn't offer one.
+     */
+    ret = arch_xen_unpopulated_init(&xen_resource);
+    if (!ret)
+        target_resource = &xen_resource;
+    else if (ret == -ENOSYS)
+        target_resource = &iomem_resource;
+    else
+        pr_err("Cannot initialize Xen resource\n");


I'd pass target_resource as a parameter to arch_xen_unpopulated_init() instead. Default routine will assign it iomem_resource and you won't have to deal with -ENOSYS.

That would be much better, thank you. Will do.





Also, what happens in case of error? Is it fatal? I don't think your changes in fill_list() will work.

The error is fatal as we don't have a suitable resource to allocate a region from, and yes, the fill_list() must not be called.





+
+    inited = true;


I agree with Stefano in that it would be better to call this from an init function, and you won't have t worry about multiple calls here.

Yes, that's good point, thank you. Will do.





-boris

--
Regards,

Oleksandr Tyshchenko