linux-kernel - [PATCH 2/2] arch/x86/xen: Silence compiler warnings

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Date:	Fri, 11 Jul 2014 21:54:21 +0200
From:	Daniel Kiper <daniel.kiper@...cle.com>
To:	linux-kernel@...r.kernel.org, x86@...nel.org,
	xen-devel@...ts.xenproject.org
Cc:	andrew.cooper3@...rix.com, boris.ostrovsky@...cle.com,
	david.vrabel@...rix.com, hpa@...or.com, ian.campbell@...rix.com,
	jbeulich@...e.com, jeremy@...p.org, konrad.wilk@...cle.com,
	matt.fleming@...el.com, mingo@...hat.com,
	stefano.stabellini@...citrix.com, tglx@...utronix.de
Subject: [PATCH 2/2] arch/x86/xen: Silence compiler warnings

Compiler complains in the following way when x86 32-bit kernel
with Xen support is build:

  CC      arch/x86/xen/enlighten.o
arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
arch/x86/xen/enlighten.c:1726:3: warning: right shift count >= width of type [enabled by default]

Such line contains following EFI initialization code:

boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);

There is no issue if x86 64-bit kernel is build. However, 32-bit case
generate warning (even if that code will not be executed because Xen
does not work on 32-bit EFI platforms) due to __pa() returning unsigned long
type which has 32-bits width. So move whole EFI initialization stuff
to separate function and build its body conditionally to avoid above
mentioned warning on x86 32-bit architecture.

Signed-off-by: Daniel Kiper <daniel.kiper@...cle.com>
---
 arch/x86/xen/enlighten.c |   35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bc89647..6abec74 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1516,12 +1516,32 @@ static void __init xen_pvh_early_guest_init(void)
 #endif
 }
 
+static void __init xen_efi_init(void)
+{
+#ifdef CONFIG_XEN_EFI
+	efi_system_table_t *efi_systab_xen;
+
+	efi_systab_xen = xen_efi_probe();
+
+	if (efi_systab_xen == NULL)
+		return;
+
+	strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
+			sizeof(boot_params.efi_info.efi_loader_signature));
+	boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
+	boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
+
+	set_bit(EFI_BOOT, &efi.flags);
+	set_bit(EFI_PARAVIRT, &efi.flags);
+	set_bit(EFI_64BIT, &efi.flags);
+#endif
+}
+
 /* First C function to be called on Xen boot */
 asmlinkage __visible void __init xen_start_kernel(void)
 {
 	struct physdev_set_iopl set_iopl;
 	int rc;
-	efi_system_table_t *efi_systab_xen;
 
 	if (!xen_start_info)
 		return;
@@ -1717,18 +1737,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
 	xen_setup_runstate_info(0);
 
-	efi_systab_xen = xen_efi_probe();
-
-	if (efi_systab_xen) {
-		strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
-				sizeof(boot_params.efi_info.efi_loader_signature));
-		boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
-		boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
-
-		set_bit(EFI_BOOT, &efi.flags);
-		set_bit(EFI_PARAVIRT, &efi.flags);
-		set_bit(EFI_64BIT, &efi.flags);
-	}
+	xen_efi_init();
 
 	/* Start the world */
 #ifdef CONFIG_X86_32
-- 
1.7.10.4

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