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From: "Jan Beulich" <JBeulich@suse.com>
To: Feng Wu <feng.wu@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>, "keir@xen.org" <keir@xen.org>,
	"george.dunlap@eu.citrix.com" <george.dunlap@eu.citrix.com>,
	"andrew.cooper3@citrix.com" <andrew.cooper3@citrix.com>,
	"dario.faggioli@citrix.com" <dario.faggioli@citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: [PATCH v2 3/4] VMX: Assign the right value to 'NDST' field in a concern case
Date: Tue, 31 May 2016 05:58:21 -0600	[thread overview]
Message-ID: <574D987D02000078000F0026@prv-mh.provo.novell.com> (raw)
In-Reply-To: <E959C4978C3B6342920538CF579893F019700A43@SHSMSX103.ccr.corp.intel.com>

>>> On 31.05.16 at 12:27, <feng.wu@intel.com> wrote:
>> From: Jan Beulich [mailto:JBeulich@suse.com]
>> Sent: Friday, May 27, 2016 10:00 PM
>> >>> On 26.05.16 at 15:39, <feng.wu@intel.com> wrote:
>> > Normally, in vmx_cpu_block() 'NDST' filed should have the same
>> > value with 'dest' or 'MASK_INSR(dest, PI_xAPIC_NDST_MASK)' depending
>> > on whether x2apic is enabled. However, in the following scenario,
>> > 'NDST' has different value:
>> >
>> > 'vcpu_block' hook gets assigned in vmx_pi_hooks_assign(), but all
>> > other three PI hooks have not been assigned or not been excuted yet.
>> > And during this interval, we are running in vmx_vcpu_block(), then
>> > 'NDST' may have different value.
>> 
>> How about simply assigning vcpu_block last? Or alternatively
>> holding pi_blocking_list_lock around all four assignments? Or
>> (maybe in addition to one of these) writing something sensible in
>> vmx_pi_hooks_assign() before doing the hook assignments? 
> 
> The problem is vmx_vcpu_block() can still get called first, since
> the other ones might not get called yet.

That refers to the first two questions, yet the third (unanswered
one) was added by me because I anticipated that response. So
what's wrong with that last option?

Jan


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  reply	other threads:[~2016-05-31 11:58 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-26 13:39 [PATCH v2 0/4] VMX: Properly handle pi descriptor and per-cpu blocking list Feng Wu
2016-05-26 13:39 ` [PATCH v2 1/4] VMX: Properly handle pi when all the assigned devices are removed Feng Wu
2016-05-27 13:43   ` Jan Beulich
2016-05-31 10:22     ` Wu, Feng
2016-05-31 11:52       ` Jan Beulich
2016-06-03  5:12         ` Wu, Feng
2016-06-03  9:45           ` Jan Beulich
2016-05-26 13:39 ` [PATCH v2 2/4] VMX: Cleanup PI per-cpu blocking list when vcpu is destroyed Feng Wu
2016-05-27 13:49   ` Jan Beulich
2016-05-31 10:22     ` Wu, Feng
2016-05-31 11:54       ` Jan Beulich
2016-05-26 13:39 ` [PATCH v2 3/4] VMX: Assign the right value to 'NDST' field in a concern case Feng Wu
2016-05-27 14:00   ` Jan Beulich
2016-05-31 10:27     ` Wu, Feng
2016-05-31 11:58       ` Jan Beulich [this message]
2016-06-03  5:23         ` Wu, Feng
2016-06-03  9:57           ` Jan Beulich
2016-06-22 18:00   ` George Dunlap
2016-06-24  9:08     ` Wu, Feng
2016-05-26 13:39 ` [PATCH v2 4/4] VMX: fixup PI descritpor when cpu is offline Feng Wu
2016-05-27 14:56   ` Jan Beulich
2016-05-31 10:31     ` Wu, Feng
2016-06-22 18:33       ` George Dunlap
2016-06-24  6:34         ` Wu, Feng
2016-05-26 17:20 ` [PATCH v2 0/4] VMX: Properly handle pi descriptor and per-cpu blocking list Dario Faggioli
2016-05-31 10:19   ` Wu, Feng
2016-06-22 21:33     ` Dario Faggioli
2016-06-24  6:33       ` Wu, Feng
2016-06-24 10:29         ` Dario Faggioli
2016-06-24 13:42           ` Wu, Feng
2016-06-24 13:49             ` George Dunlap
2016-06-24 14:36               ` Dario Faggioli

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