From patchwork Tue Sep 19 17:51:40 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John David Anglin X-Patchwork-Id: 13391752 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0575DCE79A8 for ; Tue, 19 Sep 2023 18:01:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229772AbjISSBN (ORCPT ); Tue, 19 Sep 2023 14:01:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229853AbjISSBN (ORCPT ); Tue, 19 Sep 2023 14:01:13 -0400 X-Greylist: delayed 557 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Tue, 19 Sep 2023 11:01:04 PDT Received: from dellerweb.de (dellerweb.de [173.249.48.176]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EE448F for ; Tue, 19 Sep 2023 11:01:04 -0700 (PDT) Received: from mx3210.localdomain (unknown [142.126.114.79]) by dellerweb.de (Postfix) with ESMTPSA id 3F66616002C7; Tue, 19 Sep 2023 19:51:42 +0200 (CEST) Received: by mx3210.localdomain (Postfix, from userid 1000) id A71CD22012C; Tue, 19 Sep 2023 17:51:40 +0000 (UTC) Date: Tue, 19 Sep 2023 17:51:40 +0000 From: John David Anglin To: linux-parisc@vger.kernel.org Cc: Helge Deller , James Bottomley Subject: [PATCH] parisc: Restore __ldcw_align for PA-RISC 2.0 processors Message-ID: MIME-Version: 1.0 Content-Disposition: inline Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org Back in 2005, Kyle McMartin removed the 16-byte alignment for ldcw semaphores on PA 2.0 machines (CONFIG_PA20). This broke spinlocks on pre PA8800 processors. The main symptom was random faults in mmap'd memory (e.g., gcc compilations, etc). Unfortunately, the errata for this ldcw change is lost. The issue is the 16-byte alignment required for ldcw semaphore instructions can only reduced to natural alignment when the ldcw operation can be handled coherently in cache. Only PA8800 and PA8900 processors actually support doing the operation in cache. Aligning the spinlock dynamically adds two integer instructions to each spinlock. Tested on rp3440, c8000 and a500. Signed-off-by: John David Anglin diff --git a/arch/parisc/include/asm/ldcw.h b/arch/parisc/include/asm/ldcw.h index 6d28b5514699..ee9e071859b2 100644 --- a/arch/parisc/include/asm/ldcw.h +++ b/arch/parisc/include/asm/ldcw.h @@ -2,39 +2,42 @@ #ifndef __PARISC_LDCW_H #define __PARISC_LDCW_H -#ifndef CONFIG_PA20 /* Because kmalloc only guarantees 8-byte alignment for kmalloc'd data, and GCC only guarantees 8-byte alignment for stack locals, we can't be assured of 16-byte alignment for atomic lock data even if we specify "__attribute ((aligned(16)))" in the type declaration. So, we use a struct containing an array of four ints for the atomic lock type and dynamically select the 16-byte aligned int from the array - for the semaphore. */ + for the semaphore. */ + +/* From: "Jim Hull" + I've attached a summary of the change, but basically, for PA 2.0, as + long as the ",CO" (coherent operation) completer is implemented, then the + 16-byte alignment requirement for ldcw and ldcd is relaxed, and instead + they only require "natural" alignment (4-byte for ldcw, 8-byte for + ldcd). + + Although the cache control hint is accepted by all PA 2.0 processors, + it is only implemented on PA8800/PA8900 CPUs. Prior PA8X00 CPUs still + require 16-byte alignment. If the address is unaligned, the operation + of the instruction is undefined. The ldcw instruction does not generate + unaligned data reference traps so misaligned accesses are not detected. + This hid the problem for years. So, restore the 16-byte alignment dropped + by Kyle McMartin in "Remove __ldcw_align for PA-RISC 2.0 processors". */ #define __PA_LDCW_ALIGNMENT 16 -#define __PA_LDCW_ALIGN_ORDER 4 #define __ldcw_align(a) ({ \ unsigned long __ret = (unsigned long) &(a)->lock[0]; \ __ret = (__ret + __PA_LDCW_ALIGNMENT - 1) \ & ~(__PA_LDCW_ALIGNMENT - 1); \ (volatile unsigned int *) __ret; \ }) -#define __LDCW "ldcw" -#else /*CONFIG_PA20*/ -/* From: "Jim Hull" - I've attached a summary of the change, but basically, for PA 2.0, as - long as the ",CO" (coherent operation) completer is specified, then the - 16-byte alignment requirement for ldcw and ldcd is relaxed, and instead - they only require "natural" alignment (4-byte for ldcw, 8-byte for - ldcd). */ - -#define __PA_LDCW_ALIGNMENT 4 -#define __PA_LDCW_ALIGN_ORDER 2 -#define __ldcw_align(a) (&(a)->slock) +#ifdef CONFIG_PA20 #define __LDCW "ldcw,co" - -#endif /*!CONFIG_PA20*/ +#else +#define __LDCW "ldcw" +#endif /* LDCW, the only atomic read-write operation PA-RISC has. *sigh*. We don't explicitly expose that "*a" may be written as reload diff --git a/arch/parisc/include/asm/spinlock_types.h b/arch/parisc/include/asm/spinlock_types.h index efd06a897c6a..7b986b09dba8 100644 --- a/arch/parisc/include/asm/spinlock_types.h +++ b/arch/parisc/include/asm/spinlock_types.h @@ -9,15 +9,10 @@ #ifndef __ASSEMBLY__ typedef struct { -#ifdef CONFIG_PA20 - volatile unsigned int slock; -# define __ARCH_SPIN_LOCK_UNLOCKED { __ARCH_SPIN_LOCK_UNLOCKED_VAL } -#else volatile unsigned int lock[4]; # define __ARCH_SPIN_LOCK_UNLOCKED \ { { __ARCH_SPIN_LOCK_UNLOCKED_VAL, __ARCH_SPIN_LOCK_UNLOCKED_VAL, \ __ARCH_SPIN_LOCK_UNLOCKED_VAL, __ARCH_SPIN_LOCK_UNLOCKED_VAL } } -#endif } arch_spinlock_t;