From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752047AbbBSQ4q (ORCPT ); Thu, 19 Feb 2015 11:56:46 -0500 Received: from mga02.intel.com ([134.134.136.20]:34803 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751728AbbBSQ4p (ORCPT ); Thu, 19 Feb 2015 11:56:45 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.09,609,1418112000"; d="scan'208";a="654432072" Message-ID: <1424365002.9530.138.camel@schen9-desk2.jf.intel.com> Subject: Re: [PATCH] xhci: use dma_alloc_coherent with fully cleared pages From: Tim Chen To: Mathias Nyman Cc: Sergei Shtylyov , Greg Kroah-Hartman , Jiri Slaby , "H. Peter Anvin" , Akinobu Mita , Ingo Molnar , Andrew Morton , Marek Szyprowski , Thomas Gleixner , linux-kernel@vger.kernel.org, x86@kernel.org, linux-usb@vger.kernel.org, stable , Alan Stern , ak Date: Thu, 19 Feb 2015 08:56:42 -0800 In-Reply-To: <54E5FBB1.2060300@linux.intel.com> References: <1424306081.9530.137.camel@schen9-desk2.jf.intel.com> <54E5FBB1.2060300@linux.intel.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5 (3.8.5-2.fc19) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-02-19 at 17:05 +0200, Mathias Nyman wrote: > On 19.02.2015 02:34, Tim Chen wrote: > > > > Commit d92ef66c4f8f ("x86: make dma_alloc_coherent() return zeroed memory > > if CMA is enabled") changed the dma_alloc_coherent page clearance from > > using an __GFP_ZERO in page allocation to not setting the flag but doing > > an explicit memory clear at the end. > > > > However the memory clear only covered the memory size that > > was requested, but may not be up to the full extent of the > > last page, if the total pages returned exceed the > > memory size requested. This behavior has caused problem with XHCI > > and caused it to hang: > > > > kernel: xhci_hcd 0000:00:14.0: Stopped the command ring failed, maybe the host is dead > > kernel: xhci_hcd 0000:00:14.0: Abort command ring failed > > kernel: xhci_hcd 0000:00:14.0: HC died; cleaning up > > kernel: xhci_hcd 0000:00:14.0: Error while assigning device slot ID > > kernel: xhci_hcd 0000:00:14.0: Max number of devices this xHCI host supports is 64. > > > > This patch reverts xhci the use the old behavior to avoid the hang. XHCI should > > do a proper fix to avoid this un-allocated memory. > > > > Signed-off-by: Tim Chen > > Cc: # 3.16+ > > --- > > drivers/usb/host/xhci-mem.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c > > index 5cb3d7a..39e7196 100644 > > --- a/drivers/usb/host/xhci-mem.c > > +++ b/drivers/usb/host/xhci-mem.c > > @@ -1658,7 +1658,7 @@ static int scratchpad_alloc(struct xhci_hcd *xhci, gfp_t flags) > > goto fail_sp; > > > > xhci->scratchpad->sp_array = dma_alloc_coherent(dev, > > - num_sp * sizeof(u64), > > + PAGE_ALIGN(num_sp * sizeof(u64)), > > &xhci->scratchpad->sp_dma, flags); > > if (!xhci->scratchpad->sp_array) > > goto fail_sp2; > > > > Thanks for figuring out that the issue was in allocation of scratchpad memory. > > Turns out we don't calculate the num_sp correctly in the first place, we didn't include > the additional high order field of the max scratchpad buffers xhci tells we should reserve. > I got a patch for this and will send it to forward to Greg once 3.20-rc1 is tagged > > -Mathias Great. Thanks for fixing this. Tim