Re: [PATCH v2 2/2] arch/x86/xen: Silence compiler warnings

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On July 12, 2014 5:09:48 PM EDT, Daniel Kiper <daniel.kiper@oracle.com> wrote:
>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 it conditionally to avoid above
>mentioned
>warning on x86 32-bit architecture.
>

Reviewed-by: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
>Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
>---
>v2 - suggestions/fixes:
>   - move xen_efi_init() to separate module
>     (suggested by Konrad Rzeszutek Wilk).
>---
> arch/x86/xen/Makefile    |    1 +
>arch/x86/xen/efi.c       |   43
>+++++++++++++++++++++++++++++++++++++++++++
> arch/x86/xen/enlighten.c |   15 +--------------
> arch/x86/xen/xen-ops.h   |    8 ++++++++
> 4 files changed, 53 insertions(+), 14 deletions(-)
> create mode 100644 arch/x86/xen/efi.c
>
>diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
>index 96ab2c0..7322755 100644
>--- a/arch/x86/xen/Makefile
>+++ b/arch/x86/xen/Makefile
>@@ -22,3 +22,4 @@ obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= spinlock.o
> obj-$(CONFIG_XEN_DEBUG_FS)	+= debugfs.o
> obj-$(CONFIG_XEN_DOM0)		+= apic.o vga.o
> obj-$(CONFIG_SWIOTLB_XEN)	+= pci-swiotlb-xen.o
>+obj-$(CONFIG_XEN_EFI)		+= efi.o
>diff --git a/arch/x86/xen/efi.c b/arch/x86/xen/efi.c
>new file mode 100644
>index 0000000..a02e09e
>--- /dev/null
>+++ b/arch/x86/xen/efi.c
>@@ -0,0 +1,43 @@
>+/*
>+ * Copyright (c) 2014 Oracle Co., Daniel Kiper
>+ *
>+ * This program is free software; you can redistribute it and/or
>modify
>+ * it under the terms of the GNU General Public License as published
>by
>+ * the Free Software Foundation; either version 2 of the License, or
>+ * (at your option) any later version.
>+ *
>+ * This program is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>+ * GNU General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU General Public License
>along
>+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
>+ */
>+
>+#include <linux/efi.h>
>+#include <linux/init.h>
>+#include <linux/string.h>
>+
>+#include <xen/xen-ops.h>
>+
>+#include <asm/setup.h>
>+
>+void __init xen_efi_init(void)
>+{
>+	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);
>+}
>diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
>index bc89647..2cd0463 100644
>--- a/arch/x86/xen/enlighten.c
>+++ b/arch/x86/xen/enlighten.c
>@@ -32,7 +32,6 @@
> #include <linux/gfp.h>
> #include <linux/memblock.h>
> #include <linux/edd.h>
>-#include <linux/efi.h>
> 
> #include <xen/xen.h>
> #include <xen/events.h>
>@@ -1521,7 +1520,6 @@ 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 +1715,7 @@ 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
>diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
>index c834d4b..75f98fe 100644
>--- a/arch/x86/xen/xen-ops.h
>+++ b/arch/x86/xen/xen-ops.h
>@@ -104,6 +104,14 @@ static inline void __init xen_init_apic(void)
> }
> #endif
> 
>+#ifdef CONFIG_XEN_EFI
>+extern void xen_efi_init(void);
>+#else
>+static inline void __init xen_efi_init(void)
>+{
>+}
>+#endif
>+
> /* Declare an asm function, along with symbols needed to make it
>    inlineable */
> #define DECL_ASM(ret, name, ...)		\