Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760069AbcDMLhb (ORCPT ); Wed, 13 Apr 2016 07:37:31 -0400 Received: from terminus.zytor.com ([198.137.202.10]:56186 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760053AbcDMLh1 (ORCPT ); Wed, 13 Apr 2016 07:37:27 -0400 Date: Wed, 13 Apr 2016 04:36:39 -0700 From: tip-bot for Toshi Kani Message-ID: Cc: paulmck@linux.vnet.ibm.com, mingo@kernel.org, linux-kernel@vger.kernel.org, david.vrabel@citrix.com, tglx@linutronix.de, akpm@linux-foundation.org, ying.huang@linux.intel.com, hpa@zytor.com, bp@suse.de, torvalds@linux-foundation.org, peterz@infradead.org, toshi.kani@hpe.com Reply-To: david.vrabel@citrix.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, hpa@zytor.com, ying.huang@linux.intel.com, akpm@linux-foundation.org, paulmck@linux.vnet.ibm.com, mingo@kernel.org, peterz@infradead.org, toshi.kani@hpe.com, bp@suse.de, torvalds@linux-foundation.org In-Reply-To: <1460403360-25441-1-git-send-email-toshi.kani@hpe.com> References: <1460403360-25441-1-git-send-email-toshi.kani@hpe.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/mm/pat: Fix BUG_ON() in mmap_mem() on QEMU/i386 Git-Commit-ID: 1886297ce0c8d563a08c8a8c4c0b97743e06cd37 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3323 Lines: 93 Commit-ID: 1886297ce0c8d563a08c8a8c4c0b97743e06cd37 Gitweb: http://git.kernel.org/tip/1886297ce0c8d563a08c8a8c4c0b97743e06cd37 Author: Toshi Kani AuthorDate: Mon, 11 Apr 2016 13:36:00 -0600 Committer: Ingo Molnar CommitDate: Wed, 13 Apr 2016 11:35:33 +0200 x86/mm/pat: Fix BUG_ON() in mmap_mem() on QEMU/i386 The following BUG_ON() crash was reported on QEMU/i386: kernel BUG at arch/x86/mm/physaddr.c:79! Call Trace: phys_mem_access_prot_allowed mmap_mem ? mmap_region mmap_region do_mmap vm_mmap_pgoff SyS_mmap_pgoff do_int80_syscall_32 entry_INT80_32 after commit: edfe63ec97ed ("x86/mtrr: Fix Xorg crashes in Qemu sessions") PAT is now set to disabled state when MTRRs are disabled. Thus, reactivating the __pa(high_memory) check in phys_mem_access_prot_allowed(). When CONFIG_DEBUG_VIRTUAL is set, __pa() calls __phys_addr(), which in turn calls slow_virt_to_phys() for 'high_memory'. Because 'high_memory' is set to (the max direct mapped virt addr + 1), it is not a valid virtual address. Hence, slow_virt_to_phys() returns 0 and hit the BUG_ON. Using __pa_nodebug() instead of __pa() will fix this BUG_ON. However, this code block, originally written for Pentiums and earlier, is no longer adequate since a 32-bit Xen guest has MTRRs disabled and supports ZONE_HIGHMEM. In this setup, this code sets UC attribute for accessing RAM in high memory range. Delete this code block as it has been unused for a long time. Reported-by: kernel test robot Reviewed-by: Borislav Petkov Signed-off-by: Toshi Kani Cc: Andrew Morton Cc: David Vrabel Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1460403360-25441-1-git-send-email-toshi.kani@hpe.com Link: https://lkml.org/lkml/2016/4/1/608 Signed-off-by: Ingo Molnar --- arch/x86/mm/pat.c | 19 ------------------- 1 file changed, 19 deletions(-) diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index c4c3ddc..fb0604f 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -778,25 +778,6 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn, if (file->f_flags & O_DSYNC) pcm = _PAGE_CACHE_MODE_UC_MINUS; -#ifdef CONFIG_X86_32 - /* - * On the PPro and successors, the MTRRs are used to set - * memory types for physical addresses outside main memory, - * so blindly setting UC or PWT on those pages is wrong. - * For Pentiums and earlier, the surround logic should disable - * caching for the high addresses through the KEN pin, but - * we maintain the tradition of paranoia in this code. - */ - if (!pat_enabled() && - !(boot_cpu_has(X86_FEATURE_MTRR) || - boot_cpu_has(X86_FEATURE_K6_MTRR) || - boot_cpu_has(X86_FEATURE_CYRIX_ARR) || - boot_cpu_has(X86_FEATURE_CENTAUR_MCR)) && - (pfn << PAGE_SHIFT) >= __pa(high_memory)) { - pcm = _PAGE_CACHE_MODE_UC; - } -#endif - *vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) | cachemode2protval(pcm)); return 1;