From: "Jan Beulich" <JBeulich@suse.com>
To: Paul Durrant <Paul.Durrant@citrix.com>,
Yu Zhang <yu.c.zhang@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
"Keir (Xen.org)" <keir@xen.org>,
Andrew Cooper <Andrew.Cooper3@citrix.com>,
"Tim (Xen.org)" <tim@xen.org>,
George Dunlap <George.Dunlap@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
"zhiyuan.lv@intel.com" <zhiyuan.lv@intel.com>,
"jun.nakajima@intel.com" <jun.nakajima@intel.com>
Subject: Re: [PATCH 3/3] Add HVMOP to map guest ram with p2m_ioreq_server to an ioreq server
Date: Wed, 23 Mar 2016 03:22:42 -0600 [thread overview]
Message-ID: <56F26E7202000078000DF8AF@prv-mh.provo.novell.com> (raw)
In-Reply-To: <a52cfdf42b1945868ae157844abaf060@AMSPEX02CL03.citrite.net>
>>> On 22.03.16 at 18:51, <Paul.Durrant@citrix.com> wrote:
>> From: George Dunlap [mailto:george.dunlap@citrix.com]
>> Sent: 22 March 2016 17:27
>> There's not much documentation in the code about how this is expected to
>> be used.
>>
>> For instance, having separate flags seems to imply that you can
>> independently select either read intercept, write intercept, or both;
>> but [ept_]p2m_type_to_flags() seems to assume that READ_ACCESS implies
>> WRITE_ACCESS. Do you plan to implement them separately in the future?
>> If not, would it be better to make the interface an enum instead?
>>
>> At very least it should be documented that READ_ACCESS implies
>> WRITE_ACCESS.
>
> That's not true. If WRITE_ACCESS has not been requested then writes are
> handled directly in Xen rather than being forwarded to the ioreq server. If
> h/w were to allow pages to be marked write-only then we wouldn't need to do
> that.
At least on EPT iirc you can have write-only pages, due to there
being both an R and a W bit.
>> > + p2m_memory_type_changed(d);
>> > +
>> > + rc = 0;
>> > +
>> > +out:
Btw: label placement.
Jan
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next prev parent reply other threads:[~2016-03-23 9:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-16 12:22 [PATCH 3/3] Add HVMOP to map guest ram with p2m_ioreq_server to an ioreq server Yu Zhang
2016-03-22 17:26 ` George Dunlap
2016-03-22 17:51 ` Paul Durrant
2016-03-23 9:22 ` Jan Beulich [this message]
2016-03-23 9:44 ` Yu, Zhang
2016-03-23 10:10 ` Jan Beulich
2016-03-23 10:37 ` Andrew Cooper
2016-03-23 11:43 ` George Dunlap
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