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=-8.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable 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 5A7DAC04AB3 for ; Mon, 27 May 2019 12:24:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32D6A20673 for ; Mon, 27 May 2019 12:24:37 +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="V0EcI0Rt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727165AbfE0MYg (ORCPT ); Mon, 27 May 2019 08:24:36 -0400 Received: from merlin.infradead.org ([205.233.59.134]:39798 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726280AbfE0MYf (ORCPT ); Mon, 27 May 2019 08:24:35 -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=XYW6Bv1LchMVefhh2WDoaK3VxoyotGe8j5acHUJ6YR8=; b=V0EcI0RtOJJpB+YbYiMjW84SJ RaFIbLmIDNiEbmjmJ8DGCudJ/OzXkWaMgB0SjYCi3/DWNR2QKQXFekISwvHnRrlv5ysM4blDvEEmG G5aRvcIjzAgTxPtDCbcwcocVNHxH27LL5nKZXJivG+pmRc9tyjJwXcDD/Pcc5UsVHfX7AQCbzyOpL InUesZfcRGLTQYJNF4Z9nSHl2jVqcuKpE/0rdDCn8MTWBltA9on+6DqS1/CsIT9wi1+KgL5KqnfGD SEvP3cAO6zqGahEQ4X2aX/xTt3wDDdmYzmyxKfpTmfIE2ygIJ/f4lSZeEBBY3IrczBWHIHgKBbAGj JcOcmE+qw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hVEfy-00039G-Jg; Mon, 27 May 2019 12:24:26 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 368AA20254842; Mon, 27 May 2019 14:24:25 +0200 (CEST) Date: Mon, 27 May 2019 14:24:25 +0200 From: Peter Zijlstra To: Rick Edgecombe Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, luto@kernel.org, dave.hansen@intel.com, namit@vmware.com, Meelis Roos , "David S. Miller" , Borislav Petkov , Ingo Molnar Subject: Re: [PATCH v4 2/2] vmalloc: Avoid rare case of flushing tlb with weird arguements Message-ID: <20190527122425.GQ2606@hirez.programming.kicks-ass.net> References: <20190521205137.22029-1-rick.p.edgecombe@intel.com> <20190521205137.22029-3-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521205137.22029-3-rick.p.edgecombe@intel.com> 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 Tue, May 21, 2019 at 01:51:37PM -0700, Rick Edgecombe wrote: > In a rare case, flush_tlb_kernel_range() could be called with a start > higher than the end. Most architectures should be fine with with this, but > some may not like it, so avoid doing this. > > In vm_remove_mappings(), in case page_address() returns 0 for all pages, > _vm_unmap_aliases() will be called with start = ULONG_MAX, end = 0 and > flush = 1. > > If at the same time, the vmalloc purge operation is triggered by something > else while the current operation is between remove_vm_area() and > _vm_unmap_aliases(), then the vm mapping just removed will be already > purged. In this case the call of vm_unmap_aliases() may not find any other > mappings to flush and so end up flushing start = ULONG_MAX, end = 0. So > only set flush = true if we find something in the direct mapping that we > need to flush, and this way this can't happen. > > Fixes: 868b104d7379 ("mm/vmalloc: Add flag for freeing of special permsissions") > Cc: Meelis Roos > Cc: Peter Zijlstra > Cc: "David S. Miller" > Cc: Dave Hansen > Cc: Borislav Petkov > Cc: Andy Lutomirski > Cc: Ingo Molnar > Cc: Nadav Amit > Signed-off-by: Rick Edgecombe > --- > mm/vmalloc.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 836888ae01f6..537d1134b40e 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2125,6 +2125,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) > unsigned long addr = (unsigned long)area->addr; > unsigned long start = ULONG_MAX, end = 0; > int flush_reset = area->flags & VM_FLUSH_RESET_PERMS; > + int flush_dmap = 0; > int i; > > /* > @@ -2163,6 +2164,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) > if (addr) { > start = min(addr, start); > end = max(addr + PAGE_SIZE, end); > + flush_dmap = 1; > } > } > > @@ -2172,7 +2174,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) > * reset the direct map permissions to the default. > */ > set_area_direct_map(area, set_direct_map_invalid_noflush); > - _vm_unmap_aliases(start, end, 1); > + _vm_unmap_aliases(start, end, flush_dmap); > set_area_direct_map(area, set_direct_map_default_noflush); > } Hurmph.. another clue that this range flushing is crap I feel. The phys addrs of the page array can be scattered all over the place, a range doesn't properly represent things. But yes, this seems like a minimal fix in spirit with the existing code.