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From: Joe Jin <joe.jin@oracle.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: "DONGLI.ZHANG" <dongli.zhang@oracle.com>,
	konrad@kernel.org, Christoph Helwig <hch@lst.de>,
	John Sobecki <john.sobecki@oracle.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"linux-kernel@vger.kernel.org\"" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] xen-swiotlb: exchange memory with Xen only when pages are contiguous
Date: Wed, 24 Oct 2018 09:05:30 -0700	[thread overview]
Message-ID: <b6f5e6e3-0536-d8e1-d100-aaa7f944731d@oracle.com> (raw)
In-Reply-To: <20181024130246.GA22616@localhost.localdomain>

On 10/24/18 6:02 AM, Konrad Rzeszutek Wilk wrote:
> On Tue, Oct 23, 2018 at 08:09:04PM -0700, Joe Jin wrote:
>> Commit 4855c92dbb7 "xen-swiotlb: fix the check condition for
>> xen_swiotlb_free_coherent" only fixed memory address check condition
>> on xen_swiotlb_free_coherent(), when memory was not physically
>> contiguous and tried to exchanged with Xen via 
>> xen_destroy_contiguous_region it will lead kernel panic.
> 
> s/it will lead/which lead to/?
> 
>>
>> The correct check condition should be memory is in DMA area and
>> physically contiguous.
> 
> "The correct check condition to make Xen hypercall to revert the
> memory back from its 32-bit pool is if it is:
>  1) Above its DMA bit mask (for example 32-bit devices can only address
> up to 4GB, and we may want 4GB+2K), and
>  2) If it not physically contingous

Here should be physically contiguous? on allocating, it asked physically
contiguous memory for DMA, if not contiguous, it can not do DMA,
am I right?

Andy range_straddles_page_boundary() return 0 means is physically contiguous,
is that correct?

Thanks,
Joe

> 
> N.B. The logic in the code is inverted, which leads to all sorts of
> confusions."
> 
> Does that sound correct?
> 
>>
>> Thank you Boris for pointing it out.
>>
> 
> Fixes: 4855c92dbb7 ("xen-sw..") ?
> 
>> Signed-off-by: Joe Jin <joe.jin@oracle.com>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> 
> Reported-by: Boris Ostrovs... ?
>> Cc: Christoph Helwig <hch@lst.de>
>> Cc: Dongli Zhang <dongli.zhang@oracle.com>
>> Cc: John Sobecki <john.sobecki@oracle.com>
>> ---
>>  drivers/xen/swiotlb-xen.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
>> index f5c1af4ce9ab..aed92fa019f9 100644
>> --- a/drivers/xen/swiotlb-xen.c
>> +++ b/drivers/xen/swiotlb-xen.c
>> @@ -357,8 +357,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
>>  	/* Convert the size to actually allocated. */
>>  	size = 1UL << (order + XEN_PAGE_SHIFT);
>>  
>> -	if (((dev_addr + size - 1 <= dma_mask)) ||
>> -	    range_straddles_page_boundary(phys, size))
>> +	if ((dev_addr + size - 1 <= dma_mask) &&
>> +	    !range_straddles_page_boundary(phys, size))
>>  		xen_destroy_contiguous_region(phys, order);
>>  
>>  	xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
>> -- 
>> 2.17.1 (Apple Git-112)
>>

      parent reply	other threads:[~2018-10-24 16:05 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-24  3:09 Joe Jin
2018-10-24 13:02 ` Konrad Rzeszutek Wilk
2018-10-24 13:57   ` Boris Ostrovsky
2018-10-24 14:43     ` Joe Jin
2018-10-25 11:45       ` Boris Ostrovsky
2018-10-25 14:23         ` Joe Jin
2018-10-25 16:10           ` Boris Ostrovsky
2018-10-25 16:28             ` Joe Jin
2018-10-25 18:56               ` Joe Jin
2018-10-26  7:48                 ` Christoph Helwig
2018-10-26  8:54                   ` Dongli Zhang
2018-10-26 14:48                     ` Joe Jin
2018-10-26 14:40                   ` Joe Jin
2018-10-30  2:51                 ` Joe Jin
     [not found]                   ` <57e5593233c64dc0a36c7d4c750a1ed4@AMSPEX02CL03.citrite.net>
2018-10-30 14:12                     ` [Xen-devel] " Joe Jin
     [not found]                       ` <097f1f6f16f7415aa3a52a7c4f5e52dc@AMSPEX02CL03.citrite.net>
2018-10-30 14:48                         ` Joe Jin
2018-10-24 16:05   ` Joe Jin [this message]

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