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From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	Kevin Tian <kevin.tian@intel.com>,
	Tamas Lengyel <tamas.lengyel@zentific.com>
Cc: "ian.campbell@citrix.com" <ian.campbell@citrix.com>,
	"stefano.stabellini@eu.citrix.com"
	<stefano.stabellini@eu.citrix.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Eddie Dong <eddie.dong@intel.com>,
	"ian.jackson@eu.citrix.com" <ian.jackson@eu.citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	"Aravind.Gopalakrishnan@amd.com" <Aravind.Gopalakrishnan@amd.com>,
	"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
	"boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH v6 2/4] x86/hvm: Treat non-instruction fetch nested page faults also as read violations
Date: Thu, 14 Aug 2014 21:39:41 +0100	[thread overview]
Message-ID: <53ED2C9D02000078000BA7E4@mail.emea.novell.com> (raw)
In-Reply-To: <53ECE8B0.50405@citrix.com>

>>> On 14.08.14 at 18:49, <andrew.cooper3@citrix.com> wrote:
> On 14/08/14 17:43, Tian, Kevin wrote:
>>
>> but doing so just moves from one incomplete solution (where
>> read-modify-write is not treated as read-violation) to another
>> incomplete solution (where all writes are treated read-violation). If
>> there's actual usage relying on accurate read-violation information,
>> either solution doesn't work. So I don't see the value of this change.
>>
> 
> I would agree.  Anything using this information will have to have
> detailed knowledge of what the hardware is capable of reporting, to
> understand the information it has to hand.
> 
> I think Xen should faithfully pass on what hardware reports.  It will be
> more useful to the consumer than blurring the details like this.

Not if it's unreliable. Plus on x86 elsewhere write access implies
read access anyway. If you look at the draft patch I had sent
Tamas (which I intend to rebase on his series), you'll see that
there the change here is actually strictly needed.

Jan

  parent reply	other threads:[~2014-08-14 20:39 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-11 14:48 [PATCH v6 1/4] x86: Consolidate boolean inputs in hvm and p2m into a shared bitmap Tamas K Lengyel
2014-08-11 14:48 ` [PATCH v6 2/4] x86/hvm: Treat non-instruction fetch nested page faults also as read violations Tamas K Lengyel
2014-08-11 16:04   ` Jan Beulich
2014-08-14  0:31   ` Tian, Kevin
2014-08-14  8:02     ` Tamas Lengyel
2014-08-14 16:43       ` Tian, Kevin
2014-08-14 16:49         ` Andrew Cooper
2014-08-14 17:32           ` Tamas Lengyel
2014-08-14 20:39           ` Jan Beulich [this message]
2014-08-14 22:34             ` Tian, Kevin
2014-08-14 22:59               ` Jan Beulich
2014-08-14 23:04                 ` Tian, Kevin
2014-08-14 23:08                   ` Jan Beulich
2014-08-14 23:20                     ` Tian, Kevin
2014-08-14 23:36                       ` Jan Beulich
2014-08-14 23:40                         ` Tian, Kevin
2014-08-15 14:57                           ` Jan Beulich
2014-08-15 20:17                             ` Tian, Kevin
2014-08-15 21:23                               ` Jan Beulich
2014-08-15 21:32                                 ` Tian, Kevin
2014-08-15 14:31                 ` Boris Ostrovsky
2014-08-15 15:01                   ` Jan Beulich
2014-08-15 15:09                     ` Boris Ostrovsky
2014-08-15 15:29                       ` Jan Beulich
2014-08-15 15:50                         ` Boris Ostrovsky
2014-08-15 16:33                           ` Tamas Lengyel
2014-08-15 16:48                             ` Jan Beulich
2014-08-18 19:37                               ` Tamas K Lengyel
2014-08-18 20:31                                 ` Jan Beulich
2014-08-11 14:48 ` [PATCH v6 3/4] x86/mem_event: Deliver gla fault EPT violation information Tamas K Lengyel
2014-08-11 16:08   ` Jan Beulich
2014-08-12 11:18     ` Tamas Lengyel
2014-08-12 12:10       ` Jan Beulich
2014-08-11 17:27   ` Boris Ostrovsky
2014-08-11 18:35     ` Tamas Lengyel
2014-08-11 14:48 ` [PATCH v6 4/4] tools/xen-access: Print gla valid/fault information Tamas K Lengyel
2014-08-12 15:31   ` Ian Jackson
2014-08-12 21:54     ` Tamas Lengyel
2014-08-11 16:03 ` [PATCH v6 1/4] x86: Consolidate boolean inputs in hvm and p2m into a shared bitmap Jan Beulich
2014-08-11 17:13 ` Boris Ostrovsky
2014-08-11 17:23   ` Tamas Lengyel
2014-08-14  0:18 ` Tian, Kevin
2014-08-28 12:36 ` Tim Deegan

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