linux-kernel - Re: [PATCH -next] x86/sev: Remove unused variable "err" in enforce

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Date:   Mon, 26 Sep 2022 10:52:08 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Borislav Petkov <bp@...en8.de>, Li Zetao <lizetao1@...wei.com>
CC:     tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
        x86@...nel.org, brijesh.singh@....com, michael.roth@....com,
        venu.busireddy@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] x86/sev: Remove unused variable "err" in enforce_vmpl0()

On September 26, 2022 7:48:59 AM PDT, Borislav Petkov <bp@...en8.de> wrote:
>On Sat, Sep 24, 2022 at 06:18:19PM +0800, Li Zetao wrote:
>> My Compiler version is 11.2.0. I used the default .config and compiled with
>> flags "-Wall -Werror", just as follows:
>> 
>>     make allmodconfig
>> 
>>     make EXTRA_CFLAGS="-Wall -Werror"
>
>Ah, compressed/Makefile doesn't have -Wall. That's the old problem of
>x86 not sharing makefiles. I need to dust off my patches which do that.
>
>Now, if you do:
>
>diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
>index 35ce1a64068b..10abb7c45d04 100644
>--- a/arch/x86/boot/compressed/Makefile
>+++ b/arch/x86/boot/compressed/Makefile
>@@ -34,7 +34,7 @@ targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \
> # be valid.
> KBUILD_CFLAGS := -m$(BITS) -O2 $(CLANG_FLAGS)
> KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
>-KBUILD_CFLAGS += -Wundef
>+KBUILD_CFLAGS += -Wundef -Wall
> KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
> cflags-$(CONFIG_X86_32) := -march=i386
> cflags-$(CONFIG_X86_64) := -mcmodel=small -mno-red-zone
>
>then allmodconfig triggers a bunch:
>
>arch/x86/boot/compressed/efi.c: In function ‘efi_get_system_table’:
>arch/x86/boot/compressed/efi.c:62:23: warning: unused variable ‘et’ [-Wunused-variable]
>   62 |         enum efi_type et;
>      |                       ^~
>arch/x86/boot/compressed/efi.c: In function ‘efi_get_conf_table’:
>arch/x86/boot/compressed/efi.c:134:13: warning: unused variable ‘ret’ [-Wunused-variable]
>  134 |         int ret;
>      |             ^~~
>arch/x86/boot/compressed/acpi.c: In function ‘__efi_get_rsdp_addr’:
>arch/x86/boot/compressed/acpi.c:27:13: warning: unused variable ‘ret’ [-Wunused-variable]
>   27 |         int ret;
>      |             ^~~
>arch/x86/boot/compressed/acpi.c: In function ‘efi_get_rsdp_addr’:
>arch/x86/boot/compressed/acpi.c:55:22: warning: unused variable ‘nr_tables’ [-Wunused-variable]
>   55 |         unsigned int nr_tables;
>      |                      ^~~~~~~~~
>arch/x86/boot/compressed/sev.c: In function ‘enforce_vmpl0’:
>arch/x86/boot/compressed/sev.c:256:13: warning: unused variable ‘err’ [-Wunused-variable]
>  256 |         int err;
>      |             ^~~
>
>
>Would you like to do the above instead and fix them all in one go?
>
>Thx.
>

The boot code really needs to be refactored, especially that the real-mode BIOS code is built in the root of that tree.