linux-kernel - [PATCH v2 9/9] xen/x86: adjust data placement

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Date:   Thu, 30 Sep 2021 14:21:13 +0200
From:   Jan Beulich <jbeulich@...e.com>
To:     Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:     Stefano Stabellini <sstabellini@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Roger Pau Monné <roger.pau@...rix.com>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
Subject: [PATCH v2 9/9] xen/x86: adjust data placement

Both xen_pvh and xen_start_flags get written just once early during
init. Using the respective annotation then allows the open-coded placing
in .data to go away.

Additionally the former, like the latter, wants exporting, or else
xen_pvh_domain() can't be used from modules.

Signed-off-by: Jan Beulich <jbeulich@...e.com>
---
I have to admit that it is completely unclear to me which form of
exporting I should have used: xen_domain_type is GPL-only while
xen_start_flags is not, yet both are used in similar ways, extending to
xen_pvh. Picking the GPL version was suggested by Jürgen.
---
v2: Use EXPORT_SYMBOL_GPL().

--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -75,7 +75,7 @@ EXPORT_SYMBOL_GPL(xen_have_vector_callba
  */
 enum xen_domain_type __ro_after_init xen_domain_type = XEN_NATIVE;
 EXPORT_SYMBOL_GPL(xen_domain_type);
-uint32_t xen_start_flags __section(".data") = 0;
+uint32_t __ro_after_init xen_start_flags;
 EXPORT_SYMBOL(xen_start_flags);
 
 /*
--- a/arch/x86/xen/enlighten_pvh.c
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/acpi.h>
+#include <linux/export.h>
 
 #include <xen/hvc-console.h>
 
@@ -18,10 +19,11 @@
 /*
  * PVH variables.
  *
- * The variable xen_pvh needs to live in the data segment since it is used
+ * The variable xen_pvh needs to live in a data segment since it is used
  * after startup_{32|64} is invoked, which will clear the .bss segment.
  */
-bool xen_pvh __section(".data") = 0;
+bool __ro_after_init xen_pvh;
+EXPORT_SYMBOL_GPL(xen_pvh);
 
 void __init xen_pvh_init(struct boot_params *boot_params)
 {