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[5.186.115.35]) by smtp.gmail.com with ESMTPSA id ni7sm38990ejb.57.2019.08.28.12.38.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Aug 2019 12:38:43 -0700 (PDT) From: Rasmus Villemoes To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org Cc: Rasmus Villemoes , linux-kernel@vger.kernel.org Subject: [PATCH 1/2] x86: mmu.h: move mm_context_t::lock member inside CONFIG_MODIFY_LDT_SYSCALL Date: Wed, 28 Aug 2019 21:38:35 +0200 Message-Id: <20190828193836.16791-1-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The placement of the lock member in mm_context_t suggests that it is used to protect the vdso* members, but AFAICT, it is only ever used under #ifdef CONFIG_MODIFY_LDT_SYSCALL. So guarding the member by the same config option is a cheap way to reduce sizeof(mm_struct) by 32 bytes (only for !CONFIG_MODIFY_LDT_SYSCALL kernels, of course). Signed-off-by: Rasmus Villemoes --- arch/x86/include/asm/mmu.h | 11 ++++++++--- arch/x86/include/asm/mmu_context.h | 3 +-- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index e78c7db87801..b1bb47a3577b 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -30,14 +30,13 @@ typedef struct { #ifdef CONFIG_MODIFY_LDT_SYSCALL struct rw_semaphore ldt_usr_sem; struct ldt_struct *ldt; + struct mutex lock; #endif - #ifdef CONFIG_X86_64 /* True if mm supports a task running in 32 bit compatibility mode. */ unsigned short ia32_compat; #endif - struct mutex lock; void __user *vdso; /* vdso base address */ const struct vdso_image *vdso_image; /* vdso image in use */ @@ -56,10 +55,16 @@ typedef struct { #endif } mm_context_t; +#ifdef CONFIG_MODIFY_LDT_SYSCALL +#define INIT_MM_CONTEXT_LOCK(mm) .lock = __MUTEX_INITIALIZER(mm.context.lock), +#else +#define INIT_MM_CONTEXT_LOCK(mm) +#endif + #define INIT_MM_CONTEXT(mm) \ .context = { \ .ctx_id = 1, \ - .lock = __MUTEX_INITIALIZER(mm.context.lock), \ + INIT_MM_CONTEXT_LOCK(mm) \ } void leave_mm(int cpu); diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index 9024236693d2..ac8e3ef8a774 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -82,6 +82,7 @@ static inline void init_new_context_ldt(struct mm_struct *mm) { mm->context.ldt = NULL; init_rwsem(&mm->context.ldt_usr_sem); + mutex_init(&mm->context.lock); } int ldt_dup_context(struct mm_struct *oldmm, struct mm_struct *mm); void destroy_context_ldt(struct mm_struct *mm); @@ -186,8 +187,6 @@ void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk); static inline int init_new_context(struct task_struct *tsk, struct mm_struct *mm) { - mutex_init(&mm->context.lock); - mm->context.ctx_id = atomic64_inc_return(&last_mm_ctx_id); atomic64_set(&mm->context.tlb_gen, 0); -- 2.20.1