From: Scott Wood <scottwood@freescale.com>
To: kvm-ppc@vger.kernel.org
Subject: Re: [PATCH] KVM: PPC: Not optimizing MSR_CE and MSR_DE with paravirt.
Date: Wed, 16 May 2012 22:07:20 +0000 [thread overview]
Message-ID: <4FB42518.9060401@freescale.com> (raw)
In-Reply-To: <1337067442-26625-1-git-send-email-bharat.bhushan@freescale.com>
On 05/16/2012 10:13 AM, Sethi Varun-B16395 wrote:
>>> Why is MSR[CE] unsafe?
>>
>> MSR=0
>> * critical interrupt comes in *
>> mtmsr(MSR_CE)
>> --> MSR = MSR_CE
>> * interrupt should be delivered, but host doesn't get notified that
>> MSR_CE is changing *
>>
>> However, we completely ignore critical interrupts in KVM these days, no?
Watchdog will use them.
> Well, it's least likely that MSR_CE/MSR_ME would get changed directly. They would
> mostly get changed via rfci/rfmci, which would trap.
It being unlikely means that there's little performance downside to this
patch -- it doesn't mean that this patch is unnecessary.
FWIW, Topaz directly manipulates MSR[CE] extensively, since it uses
critical interrupts as its main interrupts (to distinguish from EE
interrupts which are delivered directly to the guest).
-Scott
next prev parent reply other threads:[~2012-05-16 22:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-15 7:49 [PATCH] KVM: PPC: Not optimizing MSR_CE and MSR_DE with paravirt Bharat Bhushan
2012-05-15 14:31 ` Alexander Graf
2012-05-16 8:42 ` Bhushan Bharat-R65777
2012-05-16 9:11 ` Alexander Graf
2012-05-16 12:27 ` Sethi Varun-B16395
2012-05-16 12:47 ` Alexander Graf
2012-05-16 15:13 ` Sethi Varun-B16395
2012-05-16 22:07 ` Scott Wood [this message]
2012-05-17 11:03 ` Sethi Varun-B16395
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=4FB42518.9060401@freescale.com \
--to=scottwood@freescale.com \
--cc=kvm-ppc@vger.kernel.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.