From: Peter Xu <peterx@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Longpeng <longpeng2@huawei.com>,
Huangweidong <weidong.huang@huawei.com>,
Gonglei <arei.gonglei@huawei.com>,
wangxin <wangxinxin.wang@huawei.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH 2/4] KVM: VMX: avoid double list add with VT-d posted interrupts
Date: Fri, 9 Jun 2017 15:41:44 +0800 [thread overview]
Message-ID: <20170609074143.GL3628@pxdev.xzpeter.org> (raw)
In-Reply-To: <821f022f-ff94-876d-2426-8b6ab35af65f@redhat.com>
On Fri, Jun 09, 2017 at 09:29:45AM +0200, Paolo Bonzini wrote:
>
>
> On 09/06/2017 04:50, Peter Xu wrote:
> > Even, I'm thinking whether we can unconditionally setup PDST only in
> > pi_load(), then post_block() only needs to handle the NV bit.
>
> No, you can't do that without fiddling with the blocked_vcpu lists in
> pi_load.
Then how about we keep the blocked_vcpu list maintainance in
post_block(), but only let pi_load() handle the PDST?
(I really feel like they are two things - the blocked_vcpu list helps
for the kick when wakeup happens; while PDST makes sure the PI is
always pointing to the correct cpu)
>
> > (PS. since I'm at here... could I ask why in pi_pre_block we need to
> > udpate PDST as well? I guess that decides who will run the
> > wakeup_handler code to kick the vcpu thread, but would that really
> > matter?)
>
> For this one it's a yes. :) I think it's not needed anymore indeed
> after these patches; see this comment:
>
> /*
> * The wakeup_handler expects the VCPU to be on the
> * blocked_vcpu_list that matches ndst.
Actually I was always unclear on what this sentense means: iiuc
blocked_vcpu_list is only a list of vcpus that may need a kick, so why
it has anything to do with PDST after all?
(or say, no matter what PDST is, we just kick the vcpu thread without
doing anything else, do we?)
> Interrupts
> * are disabled so no preemption should happen, but
> * err on the side of safety.
> */
>
> So we could add a WARN.
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2017-06-09 7:41 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-06 10:57 [PATCH CFT 0/4] VT-d PI fixes Paolo Bonzini
2017-06-06 10:57 ` [PATCH 1/4] KVM: VMX: extract __pi_post_block Paolo Bonzini
2017-06-06 21:27 ` kbuild test robot
2017-06-06 10:57 ` [PATCH 2/4] KVM: VMX: avoid double list add with VT-d posted interrupts Paolo Bonzini
2017-06-06 12:30 ` Longpeng (Mike)
2017-06-06 12:35 ` Paolo Bonzini
2017-06-06 12:45 ` Longpeng (Mike)
2017-06-06 21:49 ` kbuild test robot
2017-06-08 6:50 ` Peter Xu
2017-06-08 6:53 ` Peter Xu
2017-06-08 7:00 ` Paolo Bonzini
2017-06-08 9:16 ` Peter Xu
2017-06-08 11:24 ` Paolo Bonzini
2017-06-09 2:50 ` Peter Xu
2017-06-09 7:29 ` Paolo Bonzini
2017-06-09 7:41 ` Peter Xu [this message]
2017-07-28 2:31 ` Longpeng (Mike)
2017-07-28 6:28 ` Paolo Bonzini
2017-06-06 10:57 ` [PATCH 3/4] KVM: VMX: simplify and fix vmx_vcpu_pi_load Paolo Bonzini
2017-07-28 4:22 ` Longpeng (Mike)
2017-07-28 5:14 ` Longpeng (Mike)
2017-06-06 10:57 ` [PATCH 4/4] KVM: VMX: simplify cmpxchg of PI descriptor control field Paolo Bonzini
2017-06-07 9:33 ` [PATCH CFT 0/4] VT-d PI fixes Gonglei (Arei)
2017-06-07 14:32 ` Paolo Bonzini
2017-07-11 8:55 ` Paolo Bonzini
2017-07-11 9:16 ` Gonglei (Arei)
2017-09-21 8:23 ` Longpeng (Mike)
2017-09-21 9:42 ` Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170609074143.GL3628@pxdev.xzpeter.org \
--to=peterx@redhat.com \
--cc=arei.gonglei@huawei.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=longpeng2@huawei.com \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=wangxinxin.wang@huawei.com \
--cc=weidong.huang@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).