Re: [PATCH] pci-dma: Fix x86 dma_alloc_coherent to fully clear all pages returned
From: Tim Chen
Date: Wed Feb 18 2015 - 14:40:20 EST
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
Is there any resolution on this patch? I haven't seen fixes from the
XHCI folks yet. This is breaking many of our systems.
> From: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> 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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