From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A2D6C04EBF for ; Mon, 23 Sep 2019 12:10:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 614D220835 for ; Mon, 23 Sep 2019 12:10:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Pr/sDrtt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393925AbfIWMKK (ORCPT ); Mon, 23 Sep 2019 08:10:10 -0400 Received: from merlin.infradead.org ([205.233.59.134]:41642 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387524AbfIWMKK (ORCPT ); Mon, 23 Sep 2019 08:10:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=L4tEhimko8J+iZHa8gZGRUaGzlJawq1HCtEyJj3yIJ0=; b=Pr/sDrttJStI+l6HZ3wniDRjR zHdj6VlhiyWsNITxYwv4EBg89pl6D0XTNhPtVgZ/wH50Ju9E+NusEzObbKzc2NbzHnXT0GueSgU6+ lK3FP6Jn+6qkUqC0/MjV0/8RVJRR1XwWSw8xYKXbfplKdLNa7R/0zx8AATwpZGBd2u5mrnrOhg3Iw 86IBztMyOlJ8YlOFTXotpuahPEotkxT4wBLm9j+CLnMEu5k/FRN+3t/gxHm0JXjN2pEa+NPiwdFfm QJJsyn7Cs/E6nyaJDN4ebqHUlTAdkZ6GAnjQsaauwy816kR2cBg/vPbiiA6i32nFthlmeOEpibela /7Q3zq1wA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.2 #3 (Red Hat Linux)) id 1iCNAJ-0002wp-5P; Mon, 23 Sep 2019 12:10:03 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 77B13301A7A; Mon, 23 Sep 2019 14:09:16 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7645020D80D79; Mon, 23 Sep 2019 14:10:01 +0200 (CEST) Date: Mon, 23 Sep 2019 14:10:01 +0200 From: Peter Zijlstra To: Thomas Gleixner Cc: LKML , x86@kernel.org, Andy Lutomirski , Catalin Marinas , Will Deacon , Mark Rutland , Marc Zyngier , Paolo Bonzini , kvm@vger.kernel.org, linux-arch@vger.kernel.org, jgross@suse.com Subject: Re: [RFC patch 10/15] x86/entry: Move irq tracing to C code Message-ID: <20190923121001.GG2332@hirez.programming.kicks-ass.net> References: <20190919150314.054351477@linutronix.de> <20190919150809.446771597@linutronix.de> <20190923084718.GG2349@hirez.programming.kicks-ass.net> <20190923114920.GF2332@hirez.programming.kicks-ass.net> <20190923115551.GZ2386@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190923115551.GZ2386@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 23, 2019 at 01:55:51PM +0200, Peter Zijlstra wrote: > On Mon, Sep 23, 2019 at 01:49:20PM +0200, Peter Zijlstra wrote: > > While walking the kids to school I wondered WTH we need to call > > TRACE_IRQS_OFF in the first place. If this is the return from exception > > path, interrupts had better be disabled already (in exception enter). > > > > For entry_64.S we have: > > > > - idtentry_part; which does TRACE_IRQS_OFF at the start and error_exit > > at the end. > > > > - xen_do_hypervisor_callback, xen_failsafe_callback -- which are > > confusing. > > > > So in the normal case, it appears we can simply do: > > > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > > index b7c3ea4cb19d..e9cf59ac554e 100644 > > --- a/arch/x86/entry/entry_64.S > > +++ b/arch/x86/entry/entry_64.S > > @@ -1368,8 +1368,6 @@ END(error_entry) > > > > ENTRY(error_exit) > > UNWIND_HINT_REGS > > - DISABLE_INTERRUPTS(CLBR_ANY) > > - TRACE_IRQS_OFF > > testb $3, CS(%rsp) > > jz retint_kernel > > jmp retint_user > > > > and all should be well. This leaves Xen... > > > > For entry_32.S it looks like nothing uses 'resume_userspace' so that > > ENTRY can go away. Which then leaves: > > > > * ret_from_intr: > > - common_spurious: TRACE_IRQS_OFF > > - common_interrupt: TRACE_IRQS_OFF > > - BUILD_INTERRUPT3: TRACE_IRQS_OFF > > - xen_do_upcall: ... > > > > * ret_from_exception: > > - xen_failsafe_callback: ... > > - common_exception_read_cr2: TRACE_IRQS_OFF > > - common_exception: TRACE_IRQS_OFF > > - int3: TRACE_IRQS_OFF > > > > Which again suggests: > > > > diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S > > index f83ca5aa8b77..7a19e7413a8e 100644 > > --- a/arch/x86/entry/entry_32.S > > +++ b/arch/x86/entry/entry_32.S > > @@ -825,9 +825,6 @@ END(ret_from_fork) > > cmpl $USER_RPL, %eax > > jb restore_all_kernel # not returning to v8086 or userspace > > > > -ENTRY(resume_userspace) > > - DISABLE_INTERRUPTS(CLBR_ANY) > > - TRACE_IRQS_OFF > > movl %esp, %eax > > call prepare_exit_to_usermode > > jmp restore_all > > > > with the notable exception (oh teh pun!) being Xen... _again_. > > > > With these patchlets on, we'd want prepare_exit_to_usermode() to > > validate the IRQ state, but AFAICT it _should_ all just 'work' (famous > > last words). > > > > Cc Juergen because Xen > > Arrgh.. faults!! they do local_irq_enable() but never disable them > again. Arguably those functions should be symmetric and restore IF when > they muck with it instead of relying on the exit path fixing things up. --- diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index f83ca5aa8b77..7a19e7413a8e 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -825,9 +825,6 @@ END(ret_from_fork) cmpl $USER_RPL, %eax jb restore_all_kernel # not returning to v8086 or userspace -ENTRY(resume_userspace) - DISABLE_INTERRUPTS(CLBR_ANY) - TRACE_IRQS_OFF movl %esp, %eax call prepare_exit_to_usermode jmp restore_all diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index b7c3ea4cb19d..e9cf59ac554e 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1368,8 +1368,6 @@ END(error_entry) ENTRY(error_exit) UNWIND_HINT_REGS - DISABLE_INTERRUPTS(CLBR_ANY) - TRACE_IRQS_OFF testb $3, CS(%rsp) jz retint_kernel jmp retint_user diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 4bb0f8447112..663d44c68f67 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -276,6 +276,7 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str, NOTIFY_STOP) { cond_local_irq_enable(regs); do_trap(trapnr, signr, str, regs, error_code, sicode, addr); + cond_local_irq_disable(regs); } } @@ -501,6 +502,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) die("bounds", regs, error_code); } + cond_local_irq_disable(regs); return; exit_trap: @@ -512,6 +514,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code) * time.. */ do_trap(X86_TRAP_BR, SIGSEGV, "bounds", regs, error_code, 0, NULL); + cond_local_irq_disable(regs); } dotraplinkage void @@ -525,19 +528,19 @@ do_general_protection(struct pt_regs *regs, long error_code) if (static_cpu_has(X86_FEATURE_UMIP)) { if (user_mode(regs) && fixup_umip_exception(regs)) - return; + goto exit_trap; } if (v8086_mode(regs)) { local_irq_enable(); handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code); - return; + goto exit_trap; } tsk = current; if (!user_mode(regs)) { if (fixup_exception(regs, X86_TRAP_GP, error_code, 0)) - return; + goto exit_trap; tsk->thread.error_code = error_code; tsk->thread.trap_nr = X86_TRAP_GP; @@ -549,12 +552,12 @@ do_general_protection(struct pt_regs *regs, long error_code) */ if (!preemptible() && kprobe_running() && kprobe_fault_handler(regs, X86_TRAP_GP)) - return; + goto exit_trap; if (notify_die(DIE_GPF, desc, regs, error_code, X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP) die(desc, regs, error_code); - return; + goto exit_trap; } tsk->thread.error_code = error_code; @@ -563,6 +566,8 @@ do_general_protection(struct pt_regs *regs, long error_code) show_signal(tsk, SIGSEGV, "", desc, regs, error_code); force_sig(SIGSEGV); +exit_trap: + cond_local_irq_disable(regs); } NOKPROBE_SYMBOL(do_general_protection); @@ -783,9 +788,7 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) if (v8086_mode(regs)) { handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, X86_TRAP_DB); - cond_local_irq_disable(regs); - debug_stack_usage_dec(); - goto exit; + goto exit_irq; } if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) { @@ -802,6 +805,8 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) si_code = get_si_code(tsk->thread.debugreg6); if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp) send_sigtrap(regs, error_code, si_code); + +exit_irq: cond_local_irq_disable(regs); debug_stack_usage_dec(); @@ -827,7 +832,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr) if (!user_mode(regs)) { if (fixup_exception(regs, trapnr, error_code, 0)) - return; + goto exit_trap; task->thread.error_code = error_code; task->thread.trap_nr = trapnr; @@ -835,7 +840,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr) if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) != NOTIFY_STOP) die(str, regs, error_code); - return; + goto exit_trap; } /* @@ -849,10 +854,12 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr) si_code = fpu__exception_code(fpu, trapnr); /* Retry when we get spurious exceptions: */ if (!si_code) - return; + goto exit_trap; force_sig_fault(SIGFPE, si_code, (void __user *)uprobe_get_trap_addr(regs)); +exit_trap: + cond_local_irq_disable(regs); } dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code) @@ -889,6 +896,8 @@ do_device_not_available(struct pt_regs *regs, long error_code) info.regs = regs; math_emulate(&info); + + cond_local_irq_disable(regs); return; } #endif diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9ceacd1156db..501cc36a3d6a 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1500,10 +1500,13 @@ __do_page_fault(struct pt_regs *regs, unsigned long hw_error_code, return; /* Was the fault on kernel-controlled part of the address space? */ - if (unlikely(fault_in_kernel_space(address))) + if (unlikely(fault_in_kernel_space(address))) { do_kern_addr_fault(regs, hw_error_code, address); - else + } else { do_user_addr_fault(regs, hw_error_code, address); + if (regs->flags & X86_EFLAGS_IF) + local_irq_disable(); + } } NOKPROBE_SYMBOL(__do_page_fault);