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From: "Jan Beulich" <JBeulich@suse.com>
To: Corneliu ZUZU <czuzu@bitdefender.com>
Cc: Kevin Tian <kevin.tian@intel.com>,
	Tamas K Lengyel <tamas@tklengyel.com>,
	Razvan Cojocaru <rcojocaru@bitdefender.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	xen-devel@lists.xen.org, Jun Nakajima <jun.nakajima@intel.com>
Subject: Re: [PATCH 4/7] vm-event/x86: use vm_event_vcpu_enter properly
Date: Fri, 17 Jun 2016 01:20:10 -0600	[thread overview]
Message-ID: <5763C0CA02000078000F5E70@prv-mh.provo.novell.com> (raw)
In-Reply-To: <07ba5116-1d76-a6b9-c7a6-c277c26d66b3@bitdefender.com>

>>> On 16.06.16 at 22:20, <czuzu@bitdefender.com> wrote:
> On 6/16/2016 6:00 PM, Jan Beulich wrote:
>>>>> On 16.06.16 at 16:09, <czuzu@bitdefender.com> wrote:
>>> @@ -1432,18 +1430,16 @@ static void vmx_update_guest_cr(struct vcpu *v, unsigned int cr)
>>>           if ( paging_mode_hap(v->domain) )
>>>           {
>>>               /* Manage GUEST_CR3 when CR0.PE=0. */
>>> +            uint32_t old_ctls = v->arch.hvm_vmx.exec_control;
>>>               uint32_t cr3_ctls = (CPU_BASED_CR3_LOAD_EXITING |
>>>                                    CPU_BASED_CR3_STORE_EXITING);
>>> +
>>>               v->arch.hvm_vmx.exec_control &= ~cr3_ctls;
>>>               if ( !hvm_paging_enabled(v) && !vmx_unrestricted_guest(v) )
>>>                   v->arch.hvm_vmx.exec_control |= cr3_ctls;
>>>   
>>> -            /* Trap CR3 updates if CR3 memory events are enabled. */
>>> -            if ( v->domain->arch.monitor.write_ctrlreg_enabled &
>>> -                 monitor_ctrlreg_bitmask(VM_EVENT_X86_CR3) )
>>> -                v->arch.hvm_vmx.exec_control |= CPU_BASED_CR3_LOAD_EXITING;
>>> -
>>> -            vmx_update_cpu_exec_control(v);
>>> +            if ( old_ctls != v->arch.hvm_vmx.exec_control )
>>> +                vmx_update_cpu_exec_control(v);
>>>           }
>> How does this match up with the rest of this patch?
> 
> And by 'this' you mean slightly optimizing this sequence by adding in 
> old_ctls?
> It seems pretty straight-forward to me, I figured if I am to move the 
> monitor.write_ctrlreg_enabled part from here
> it wouldn't be much of a stretch to also do this little 
> optimization...what would have been appropriate?
> To do this in a separate patch? To mention it in the commit message?

At least the latter, and perhaps better the former. Without even
mentioning it the readers (reviewers) have to guess whether this
is an integral part of the change, or - as you now confirm - just a
minor optimization done along the road.

Jan


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  reply	other threads:[~2016-06-17  7:20 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-16 14:04 [PATCH 0/7] vm-event: Implement ARM support for control-register writes Corneliu ZUZU
2016-06-16 14:06 ` [PATCH 1/7] minor (formatting) fixes Corneliu ZUZU
2016-06-16 14:24   ` Jan Beulich
2016-06-16 19:19     ` Corneliu ZUZU
2016-06-17  7:06       ` Jan Beulich
2016-06-17 10:46         ` Corneliu ZUZU
2016-06-16 16:02   ` Tamas K Lengyel
2016-06-17  8:33     ` Corneliu ZUZU
2016-06-17  8:36       ` Razvan Cojocaru
2016-06-17  9:29         ` Andrew Cooper
2016-06-17  9:35           ` Jan Beulich
2016-06-17  9:33         ` Jan Beulich
2016-06-17  9:36           ` Razvan Cojocaru
2016-06-17  9:40             ` Jan Beulich
2016-06-17  9:42               ` Razvan Cojocaru
2016-06-17 19:05           ` Tamas K Lengyel
2016-06-16 14:07 ` [PATCH 2/7] vm-event: VM_EVENT_FLAG_DENY requires VM_EVENT_FLAG_VCPU_PAUSED Corneliu ZUZU
2016-06-16 16:11   ` Tamas K Lengyel
2016-06-17  8:43     ` Corneliu ZUZU
2016-06-21 11:26     ` Corneliu ZUZU
2016-06-21 15:09       ` Tamas K Lengyel
2016-06-22  8:34         ` Corneliu ZUZU
2016-06-16 14:08 ` [PATCH 3/7] vm-event: introduce vm_event_vcpu_enter Corneliu ZUZU
2016-06-16 14:51   ` Jan Beulich
2016-06-16 20:10     ` Corneliu ZUZU
2016-06-16 20:33       ` Razvan Cojocaru
2016-06-17 10:41         ` Corneliu ZUZU
2016-06-17  7:17       ` Jan Beulich
2016-06-17 11:13         ` Corneliu ZUZU
2016-06-17 11:27           ` Jan Beulich
2016-06-17 12:13             ` Corneliu ZUZU
2016-06-16 16:17   ` Tamas K Lengyel
2016-06-17  9:19     ` Corneliu ZUZU
2016-06-17  8:55   ` Julien Grall
2016-06-17 11:40     ` Corneliu ZUZU
2016-06-17 13:22       ` Julien Grall
2016-06-16 14:09 ` [PATCH 4/7] vm-event/x86: use vm_event_vcpu_enter properly Corneliu ZUZU
2016-06-16 15:00   ` Jan Beulich
2016-06-16 20:20     ` Corneliu ZUZU
2016-06-17  7:20       ` Jan Beulich [this message]
2016-06-17 11:23         ` Corneliu ZUZU
2016-06-16 16:27   ` Tamas K Lengyel
2016-06-17  9:24     ` Corneliu ZUZU
2016-06-16 14:10 ` [PATCH 5/7] x86: replace monitor_write_data.do_write with enum Corneliu ZUZU
2016-06-16 14:12 ` [PATCH 6/7] vm-event/arm: move hvm_event_cr->common vm_event_monitor_cr Corneliu ZUZU
2016-06-16 15:16   ` Jan Beulich
2016-06-17  8:25     ` Corneliu ZUZU
2016-06-17  8:38       ` Jan Beulich
2016-06-17 11:31         ` Corneliu ZUZU
2016-06-21  7:08       ` Corneliu ZUZU
2016-06-21  7:20         ` Jan Beulich
2016-06-21 15:22           ` Tamas K Lengyel
2016-06-22  6:33             ` Jan Beulich
2016-06-16 16:55   ` Tamas K Lengyel
2016-06-17 10:37     ` Corneliu ZUZU
2016-06-16 14:13 ` [PATCH 7/7] vm-event/arm: implement support for control-register write vm-events Corneliu ZUZU
2016-06-16 14:26   ` Julien Grall
2016-06-16 19:24     ` Corneliu ZUZU
2016-06-16 21:28       ` Julien Grall
2016-06-17 11:46         ` Corneliu ZUZU
2016-06-16 16:49   ` Julien Grall
2016-06-17 10:36     ` Corneliu ZUZU
2016-06-17 13:18       ` Julien Grall
2016-06-22 16:35       ` Corneliu ZUZU
2016-06-22 17:17         ` Julien Grall
2016-06-22 18:39           ` Corneliu ZUZU
2016-06-22 19:37             ` Corneliu ZUZU
2016-06-22 19:41               ` Julien Grall
2016-06-23  5:31                 ` Corneliu ZUZU
2016-06-23  5:49                   ` Corneliu ZUZU
2016-06-23 11:11                     ` Julien Grall
2016-06-24  9:32                       ` Corneliu ZUZU
2016-06-23 11:00           ` Julien Grall

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