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From: "Jan Beulich" <JBeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
	Julien Grall <julien.grall@arm.com>
Subject: Re: [PATCH] x86/HVM: correct notion of new CPL in task switch emulation
Date: Tue, 06 Jun 2017 00:42:20 -0600	[thread overview]
Message-ID: <59366AEC020000780015F97E@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1e7526dd-8ee1-bdbd-38c3-13d691d03c7e@citrix.com>

>>> On 05.06.17 at 15:06, <andrew.cooper3@citrix.com> wrote:
> On 01/06/17 13:11, Jan Beulich wrote:
>> Commit aac1df3d03 ("x86/HVM: introduce hvm_get_cpl() and respective
>> hook") went too far in one aspect: When emulating a task switch we
>> really shouldn't be looking at what hvm_get_cpl() returns, as we're
>> switching all segment registers.
>>
>> However, instead of reverting the relevant parts of that commit, have
>> the caller tell the segment loading function what the new CPL is. This
>> at once fixes ES being loaded before CS so far having had its checks
>> done against the old CPL.
>>
>> Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> 
> On further consideration, wouldn't it be better to audit all segment
> registers, before updating any of them in the vmcs/vmcb?  This would
> leave us with a far lower chance of other vmentry failures.

Overall yes (and I did make a not on my todo list), but I think we
want to address the regression with no meaningful re-work right
now.

Jan



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  reply	other threads:[~2017-06-06  6:42 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-01 12:11 [PATCH] x86/HVM: correct notion of new CPL in task switch emulation Jan Beulich
2017-06-02 20:02 ` Andrew Cooper
2017-06-02 20:33   ` Andrew Cooper
2017-06-06  7:06     ` Jan Beulich
2017-06-06 10:21       ` Andrew Cooper
2017-06-06 17:14   ` Julien Grall
2017-06-05 13:06 ` Andrew Cooper
2017-06-06  6:42   ` Jan Beulich [this message]
2017-06-06 10:21     ` Andrew Cooper

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