From: Gleb Natapov <gleb@redhat.com>
To: "Zhang, Yang Z" <yang.z.zhang@intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"Tian, Kevin" <kevin.tian@intel.com>
Subject: Re: [PATCH v3 3/4] x86, apicv: add virtual interrupt delivery support
Date: Fri, 7 Dec 2012 09:28:23 +0200 [thread overview]
Message-ID: <20121207072823.GF14176@redhat.com> (raw)
In-Reply-To: <A9667DDFB95DB7438FA9D7D576C3D87E2D6AD9@SHSMSX101.ccr.corp.intel.com>
On Fri, Dec 07, 2012 at 01:00:18AM +0000, Zhang, Yang Z wrote:
> Marcelo Tosatti wrote on 2012-12-07:
> >>> How about to recaculate irr_pending according the VIRR on each vmexit?
> >>>
> >> No need really. Since HW can only clear VIRR the only situation that may
> >> happen is that irr_pending will be true but VIRR is empty and
> >> apic_find_highest_irr() will return correct result in this case.
> >>
> >> If we will see a lot of unneeded irr scans because of stale irr_pending
> >> value we can do irr_pending = rvi != 0 on vmexit.
> >>
> >> --
> >> Gleb.
> >
> > Yes, it is harmless ATM. But its clearer if irr_pending is not used when
> > virtual interrupt delivery is in effect (that is, just skip irr_pending
> > if virtual interrupt delivery is enabled).
> irr_pending still is useful in virtual interrupt delivery case. Or else, as gleb said ,there may be lots of unneeded irr scan.
>
Actually, looking at it close, irr_pending will always be true (and
thus effectively disabled without any additional checks) since it is
cleared only in kvm_get_apic_interrupt() which will not be called with
vid enabled. It is racy to do irr_pending = rvi != 0 on vmexit either.
The code should be something like that:
irr_pending = (rvi != 0) ? : apic_search_irr(apic) != -1;
But we do not want to do that on each exit since rvi will be mostly
zero and irr is, more often than not, empty.
--
Gleb.
next prev parent reply other threads:[~2012-12-07 7:28 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-03 7:01 [PATCH v3 0/4] x86, apicv: Add APIC virtualization support Yang Zhang
2012-12-03 7:01 ` [PATCH v3 1/4] x86: PIT connects to pin 2 of IOAPIC Yang Zhang
2012-12-03 9:42 ` Gleb Natapov
2012-12-04 5:32 ` Zhang, Yang Z
2012-12-04 12:55 ` Gleb Natapov
2012-12-05 1:28 ` Zhang, Yang Z
2012-12-03 7:01 ` [PATCH v3 2/4] x86, apicv: add APICv register virtualization support Yang Zhang
2012-12-05 0:29 ` Marcelo Tosatti
2012-12-05 3:17 ` Zhang, Yang Z
2012-12-05 23:11 ` Marcelo Tosatti
2012-12-06 6:45 ` Gleb Natapov
2012-12-03 7:01 ` [PATCH v3 3/4] x86, apicv: add virtual interrupt delivery support Yang Zhang
2012-12-03 11:37 ` Gleb Natapov
2012-12-04 6:39 ` Zhang, Yang Z
2012-12-04 10:58 ` Gleb Natapov
2012-12-05 1:55 ` Zhang, Yang Z
2012-12-05 5:02 ` Gleb Natapov
2012-12-05 6:02 ` Zhang, Yang Z
2012-12-05 10:18 ` Gleb Natapov
2012-12-05 13:51 ` Zhang, Yang Z
2012-12-05 14:00 ` Gleb Natapov
2012-12-06 2:55 ` Zhang, Yang Z
2012-12-06 7:07 ` Gleb Natapov
2012-12-06 7:16 ` Zhang, Yang Z
2012-12-06 7:19 ` Gleb Natapov
2012-12-06 7:20 ` Zhang, Yang Z
2012-12-04 16:46 ` Michael S. Tsirkin
2012-12-05 2:00 ` Marcelo Tosatti
2012-12-05 3:43 ` Zhang, Yang Z
2012-12-05 11:14 ` Gleb Natapov
2012-12-05 14:16 ` Zhang, Yang Z
2012-12-05 14:34 ` Gleb Natapov
2012-12-06 2:58 ` Zhang, Yang Z
2012-12-05 22:38 ` Marcelo Tosatti
2012-12-06 9:28 ` Gleb Natapov
2012-12-06 11:35 ` Zhang, Yang Z
2012-12-05 22:31 ` Marcelo Tosatti
2012-12-06 3:31 ` Zhang, Yang Z
2012-12-06 5:02 ` Zhang, Yang Z
2012-12-06 6:36 ` Gleb Natapov
2012-12-06 6:56 ` Zhang, Yang Z
2012-12-06 20:08 ` Marcelo Tosatti
2012-12-07 1:00 ` Zhang, Yang Z
2012-12-07 7:28 ` Gleb Natapov [this message]
2012-12-03 7:01 ` [PATCH v3 4/4] x86, apicv: add virtual x2apic support Yang Zhang
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=20121207072823.GF14176@redhat.com \
--to=gleb@redhat.com \
--cc=kevin.tian@intel.com \
--cc=kvm@vger.kernel.org \
--cc=mtosatti@redhat.com \
--cc=yang.z.zhang@intel.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).