linux-kernel - Re: [Xen-devel] [PATCH 0/2] block/xen-blkfront: Support non-indirect with 64KB page granularity

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Date:	Mon, 14 Sep 2015 08:37:06 +0800
From:	Bob Liu <bob.liu@...cle.com>
To:	Julien Grall <julien.grall@...rix.com>
CC:	xen-devel@...ts.xenproject.org, ian.campbell@...rix.com,
	stefano.stabellini@...citrix.com, linux-kernel@...r.kernel.org,
	David Vrabel <david.vrabel@...rix.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Roger Pau Monné 
	<roger.pau@...rix.com>
Subject: Re: [Xen-devel] [PATCH 0/2] block/xen-blkfront: Support non-indirect
 with 64KB page granularity



On 09/14/2015 01:47 AM, Julien Grall wrote:
> 
> 
> On 13/09/2015 13:44, Bob Liu wrote:
>> I may misunderstood here.
>> But I think same changes are also required even if backend supports indirect grant when frontend is using 64KB page granularity.
>> Else
>> 1) How to set up the grant map for requests in domU?
>> The minimum segment buffer size in a request is PAGE_SIZE(64KB) while grant is 4KB based.
>>
>> 2) Codes like below in blkback.c may not work correctly?
>> if ((req->u.rw.seg[i].last_sect >= (PAGE_SIZE >> 9)) ||
>>
>> Because PAGE_SIZE in backend is 4KB, while the written value by domU is 64KB based.
> 
> As mention in my cover letter, this patch is not self-sufficient to support 64KB guest. It's a follow-up of the 64KB page granularity support I sent on the ML (the new version was sent earlier this week [1]).
> 
> One of the patch [2] is taking care of breaking down the I/O request in multiple 4KB segment that will be used in the ring request. You may want to give a look to this patch before looking to this series.
> 

Oh, sorry! I'll have a look at those patches.

Thanks,
-Bob
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