Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933370AbbBBOCf (ORCPT ); Mon, 2 Feb 2015 09:02:35 -0500 Received: from mail-wg0-f41.google.com ([74.125.82.41]:54428 "EHLO mail-wg0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754233AbbBBOCc (ORCPT ); Mon, 2 Feb 2015 09:02:32 -0500 Message-ID: <54CF8374.80704@suse.cz> Date: Mon, 02 Feb 2015 15:02:28 +0100 From: Jiri Slaby User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Tim Chen , Sergei Shtylyov CC: "H. Peter Anvin" , Akinobu Mita , Mathias Nyman , Andi Kleen , Ingo Molnar , Andrew Morton , Marek Szyprowski , Thomas Gleixner , linux-kernel@vger.kernel.org, x86@kernel.org, linux-usb@vger.kernel.org, stable Subject: Re: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all pages returned References: <1422647641.9530.2.camel@schen9-desk2.jf.intel.com> <54CBF1A0.9080005@cogentembedded.com> <1422654849.9530.8.camel@schen9-desk2.jf.intel.com> In-Reply-To: <1422654849.9530.8.camel@schen9-desk2.jf.intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2649 Lines: 83 On 01/30/2015, 10:54 PM, Tim Chen wrote: > On Sat, 2015-01-31 at 00:03 +0300, Sergei Shtylyov wrote: >> On 01/30/2015 10:54 PM, Tim Chen wrote: > >>> >>> return NULL; >>> } >>> + /* round up to full page size */ >>> + size = (((size-1) >> PAGE_SHIFT) + 1) * PAGE_SIZE; >> >> This is quite suboptimal formula, we can do without shifts and >> multiplications (hopefully, still converted to shifts by gcc): >> >> size = (size + ~PAGE_MASK) & PAGE_MASK; > > Agree. I've updated patch below > > Thanks. > > Tim > > --->8--- > > From: Tim Chen > Subject: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all pages returned > > > 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. > > Other drivers may have similar issue if it assumes that the pages > allocated are completely zeroed. > > This patch ensures that the pages returned are fully cleared. > > Signed-off-by: Tim Chen > Cc: # 3.16+ > > --- > arch/x86/kernel/pci-dma.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c > index a25e202..e9d8dee 100644 > --- a/arch/x86/kernel/pci-dma.c > +++ b/arch/x86/kernel/pci-dma.c > @@ -125,6 +125,8 @@ again: > > return NULL; > } > + /* round up to full page size */ > + size = (size + ~PAGE_MASK) & PAGE_MASK; Hi, is this an open-coded version of PAGE_ALIGN? > memset(page_address(page), 0, size); > *dma_addr = addr; > return page_address(page); > -- js suse labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/