Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752685AbaGKUbE (ORCPT ); Fri, 11 Jul 2014 16:31:04 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:41590 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751934AbaGKUbC (ORCPT ); Fri, 11 Jul 2014 16:31:02 -0400 Message-ID: <53C049DB.3050904@oracle.com> Date: Fri, 11 Jul 2014 16:32:27 -0400 From: Boris Ostrovsky User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Daniel Kiper CC: linux-kernel@vger.kernel.org, x86@kernel.org, xen-devel@lists.xenproject.org, andrew.cooper3@citrix.com, david.vrabel@citrix.com, hpa@zytor.com, ian.campbell@citrix.com, jbeulich@suse.com, jeremy@goop.org, konrad.wilk@oracle.com, matt.fleming@intel.com, mingo@redhat.com, stefano.stabellini@eu.citrix.com, tglx@linutronix.de Subject: Re: [PATCH 2/2] arch/x86/xen: Silence compiler warnings References: <1405108461-3223-1-git-send-email-daniel.kiper@oracle.com> <1405108461-3223-3-git-send-email-daniel.kiper@oracle.com> <53C04322.1050000@oracle.com> <20140711201050.GJ13620@olila.local.net-space.pl> In-Reply-To: <20140711201050.GJ13620@olila.local.net-space.pl> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/11/2014 04:10 PM, Daniel Kiper wrote: > On Fri, Jul 11, 2014 at 04:03:46PM -0400, Boris Ostrovsky wrote: >> On 07/11/2014 03:54 PM, Daniel Kiper 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 its body conditionally to avoid above >>> mentioned warning on x86 32-bit architecture. >>> >>> Signed-off-by: Daniel Kiper >>> --- >>> 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(); >> I'd put ifdef CONFIG_XEN_EFI around the call instead of having it >> inside the routine. > Well, I thought about that a bit and I prefer function like Konrad. > Could you agree with him which solution do you (as maintainers) prefer? > I am not arguing against having a separate routine. All I am saying is that calling xen_efi_init() when CONFIG_XEN_EFI is not defined doesn't look logical. It will also add an unnecessary call (although compiler may optimize it out). -boris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/