linux-kernel - Re: [PATCH UPSTREAM] xen-swiotlb: fix the check condition for xen_swiotlb_free

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Date:   Thu, 17 May 2018 12:32:37 -0700
From:   Joe Jin <joe.jin@...cle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        John Sobecki <john.sobecki@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        ASHISH_B_SRIVASTAVA <ashish.b.srivastava@...cle.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH UPSTREAM] xen-swiotlb: fix the check condition for
 xen_swiotlb_free_coherent

On 5/17/18 12:10 PM, Greg KH wrote:
> On Thu, May 17, 2018 at 11:45:57AM -0700, Joe Jin wrote:
>> When run raidconfig from Dom0 we found that the Xen DMA heap is reduced,
>> but Dom Heap is increased by the same size. Tracing raidconfig we found
>> that the related ioctl() in megaraid_sas will call dma_alloc_coherent()
>> to apply memory. If the memory allocated by Dom0 is not in the DMA area,
>> it will exchange memory with Xen to meet the requiment. Later drivers
>> call dma_free_coherent() to free the memory, on xen_swiotlb_free_coherent()
>> the check condition (dev_addr + size - 1 <= dma_mask) is always false,
>> it prevents calling xen_destroy_contiguous_region() to return the memory
>> to the Xen DMA heap.
>>
>> This issue introduced by commit 6810df88dcfc2 "xen-swiotlb: When doing
>> coherent alloc/dealloc check before swizzling the MFNs.".
>>
>> Signed-off-by: Joe Jin <joe.jin@...cle.com>
>> Tested-by: John Sobecki <john.sobecki@...cle.com> 
>> Reviewed-by: Rzeszutek Wilk <konrad.wilk@...cle.com>
>> Cc: stable@...r.kernel.org
>> ---
>>  drivers/xen/swiotlb-xen.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> What does "PATCH UPSTREAM" mean?

Oops I forgot to remove UPSTREAM, the tag for internal review.

Sorry for this, will resend it without the tag.

Thanks,
Joe

> 
> confused,
> 
> greg k-h
>