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

From: Bob Liu <bob.liu@oracle.com>
To: Julien Grall <julien.grall@citrix.com>
Cc: xen-devel@lists.xenproject.org, ian.campbell@citrix.com,
	stefano.stabellini@eu.citrix.com, linux-kernel@vger.kernel.org,
	"David Vrabel" <david.vrabel@citrix.com>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 0/2] block/xen-blkfront: Support non-indirect with 64KB page granularity
Date: Mon, 14 Sep 2015 08:37:06 +0800	[thread overview]
Message-ID: <55F616B2.2070703@oracle.com> (raw)
In-Reply-To: <55F5B6BD.4030904@citrix.com>

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