From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752384AbcAEReA (ORCPT ); Tue, 5 Jan 2016 12:34:00 -0500 Received: from foss.arm.com ([217.140.101.70]:59527 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751667AbcAERd6 (ORCPT ); Tue, 5 Jan 2016 12:33:58 -0500 From: Mark Rutland To: cmetcalf@ezchip.com Cc: mark.rutland@arm.com, will.deacon@arm.com, catalin.marinas@arm.com, luto@amacapital.net, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 1/2] arm64: entry: remove pointless SPSR mode check Date: Tue, 5 Jan 2016 17:33:34 +0000 Message-Id: <1452015215-29506-1-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <20160105172106.GA7088@leverpostej> References: <20160105172106.GA7088@leverpostej> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In work_pending we may skip work if the stacked SPSR value represents anything other than an EL0 context. We then immediately invoke the kernel_exit 0 macro as part of ret_to_user, assuming a return to EL0. This is somewhat confusing. We use work_pending as part of the ret_to_user/ret_fast_syscall state machine. We only use ret_fast_syscall in the return from an SVC issued from EL0. We use ret_to_user for return from EL0 exception handlers and also for return from ret_from_fork in the case the task was not a kernel thread (i.e. it is a user task). Thus in all cases the stacked SPSR value must represent an EL0 context, and the check is redundant. This patch removes it, along with the now unused no_work_pending label. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Chris Metcalf Cc: Will Deacon --- arch/arm64/kernel/entry.S | 4 ---- 1 file changed, 4 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 7ed3d75..6b30ab1 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -626,10 +626,7 @@ ret_fast_syscall_trace: work_pending: tbnz x1, #TIF_NEED_RESCHED, work_resched /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */ - ldr x2, [sp, #S_PSTATE] mov x0, sp // 'regs' - tst x2, #PSR_MODE_MASK // user mode regs? - b.ne no_work_pending // returning to kernel enable_irq // enable interrupts for do_notify_resume() bl do_notify_resume b ret_to_user @@ -645,7 +642,6 @@ ret_to_user: and x2, x1, #_TIF_WORK_MASK cbnz x2, work_pending enable_step_tsk x1, x2 -no_work_pending: kernel_exit 0 ENDPROC(ret_to_user) -- 1.9.1 From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Tue, 5 Jan 2016 17:33:34 +0000 Subject: [PATCH 1/2] arm64: entry: remove pointless SPSR mode check In-Reply-To: <20160105172106.GA7088@leverpostej> References: <20160105172106.GA7088@leverpostej> Message-ID: <1452015215-29506-1-git-send-email-mark.rutland@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org In work_pending we may skip work if the stacked SPSR value represents anything other than an EL0 context. We then immediately invoke the kernel_exit 0 macro as part of ret_to_user, assuming a return to EL0. This is somewhat confusing. We use work_pending as part of the ret_to_user/ret_fast_syscall state machine. We only use ret_fast_syscall in the return from an SVC issued from EL0. We use ret_to_user for return from EL0 exception handlers and also for return from ret_from_fork in the case the task was not a kernel thread (i.e. it is a user task). Thus in all cases the stacked SPSR value must represent an EL0 context, and the check is redundant. This patch removes it, along with the now unused no_work_pending label. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Chris Metcalf Cc: Will Deacon --- arch/arm64/kernel/entry.S | 4 ---- 1 file changed, 4 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 7ed3d75..6b30ab1 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -626,10 +626,7 @@ ret_fast_syscall_trace: work_pending: tbnz x1, #TIF_NEED_RESCHED, work_resched /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */ - ldr x2, [sp, #S_PSTATE] mov x0, sp // 'regs' - tst x2, #PSR_MODE_MASK // user mode regs? - b.ne no_work_pending // returning to kernel enable_irq // enable interrupts for do_notify_resume() bl do_notify_resume b ret_to_user @@ -645,7 +642,6 @@ ret_to_user: and x2, x1, #_TIF_WORK_MASK cbnz x2, work_pending enable_step_tsk x1, x2 -no_work_pending: kernel_exit 0 ENDPROC(ret_to_user) -- 1.9.1