From: "Jan Beulich" <JBeulich@suse.com>
To: Feng Wu <feng.wu@intel.com>
Cc: kevin.tian@intel.com, keir@xen.org, george.dunlap@eu.citrix.com,
andrew.cooper3@citrix.com, dario.faggioli@citrix.com,
xen-devel@lists.xen.org
Subject: Re: [PATCH v2 3/4] VMX: Assign the right value to 'NDST' field in a concern case
Date: Fri, 27 May 2016 08:00:04 -0600 [thread overview]
Message-ID: <57486F0402000078000EF404@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1464269954-8056-4-git-send-email-feng.wu@intel.com>
>>> 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? Of
course much depends on whether the ASSERT() you replace was
meant just as a sanity check, or instead logic elsewhere relies on
NDST having the right value already before getting into
vmx_vcpu_block().
Also, rather than saying twice that NDST has a different value in
that case, how about stating what exact value it has then and
why that's not what we want/need? (Same goes for the code
comment then.)
> This patch fix this concern case.
Here as well as in earlier patches - do you perhaps mean "corner
case"?
Jan
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next prev parent reply other threads:[~2016-05-27 14:00 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 [this message]
2016-05-31 10:27 ` Wu, Feng
2016-05-31 11:58 ` Jan Beulich
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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