linux-kernel - Re: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all pages returned

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Message-ID: <1424288411.9530.119.camel@schen9-desk2.jf.intel.com>
Date:	Wed, 18 Feb 2015 11:40:11 -0800
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, "H. Peter Anvin" <hpa@...or.com>,
	Akinobu Mita <akinobu.mita@...il.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-usb@...r.kernel.org, stable <stable@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all
 pages returned

On Wed, 2015-02-04 at 10:30 -0800, Tim Chen wrote:
> On Mon, 2015-02-02 at 19:39 +0300, Sergei Shtylyov wrote:
> 
> > 
> > > Hi, is this an open-coded version of PAGE_ALIGN?
> > 
> >     Yes, it appears so. :-)
> > 
> > WBR, Sergei
> > 
> 
> Thanks for the suggestion by Jiri. I updated the patch to use PAGE_ALIGN
> below.
> 
> Regards,
> Tim
> 

Is there any resolution on this patch?  I haven't seen fixes from the
XHCI folks yet.  This is breaking many of our systems.

Thanks.

Tim

> --->8---
> From: Tim Chen <tim.c.chen@...ux.intel.com>
> 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 <tim.c.chen@...ux.intel.com>
> Cc: stable@...r.kernel.org
> ---
>  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..3bdee55 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 = PAGE_ALIGN(size);
>  	memset(page_address(page), 0, size);
>  	*dma_addr = addr;
>  	return page_address(page);


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