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From: "Jan Beulich" <JBeulich@suse.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
	"ian.campbell@citrix.com" <ian.campbell@citrix.com>,
	"stefano.stabellini@eu.citrix.com"
	<stefano.stabellini@eu.citrix.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	"ian.jackson@eu.citrix.com" <ian.jackson@eu.citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Eddie Dong <eddie.dong@intel.com>,
	"Aravind.Gopalakrishnan@amd.com" <Aravind.Gopalakrishnan@amd.com>,
	"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
	Tamas Lengyel <tamas.lengyel@zentific.com>
Subject: Re: [PATCH v6 2/4] x86/hvm: Treat non-instruction fetch nested page faults also as read violations
Date: Fri, 15 Aug 2014 16:01:22 +0100	[thread overview]
Message-ID: <53EE2ED202000078000BA8D3@mail.emea.novell.com> (raw)
In-Reply-To: <53EE19AE.1010000@oracle.com>

>>> On 15.08.14 at 16:31, <boris.ostrovsky@oracle.com> wrote:
> On 08/14/2014 06:59 PM, Jan Beulich wrote:
>> No - the hardware specifically does _not_ guarantee to report the
>> actual characteristics of a read-modify-write instruction. Or at least
>> that's what your documentation warns about. And to be on the safe
>> side, treating all writes as also being reads is the better option than
>> to mistakenly treat r-m-w as just w.
> 
> Is this specific to VMX or does SVM have the same problem (I am not 
> aware of this but I might be wrong). Because if it doesn't then I think 
> Tamas' [PATCH v6 2/4] should have SVM report actual bits.

You as the SVM maintainer should know better than me... With
NPT using "normal" page fault error codes, there is not even an
indication for read access. Tamas's patches adjust the current
misbehavior too in that at least instruction fetches no longer get
reported as reads.

Jan

  reply	other threads:[~2014-08-15 15:01 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
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 [this message]
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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