On 05/16/2012 02:27 PM, Sethi Varun-B16395 wrote:
-----Original Message-----
From: kvm-ppc-owner@xxxxxxxxxxxxxxx [mailto:kvm-ppc-
owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf
Sent: Wednesday, May 16, 2012 2:42 PM
To: Bhushan Bharat-R65777
Cc: kvm-ppc@xxxxxxxxxxxxxxx
Subject: Re: [PATCH] KVM: PPC: Not optimizing MSR_CE and MSR_DE with
paravirt.
On 05/16/2012 10:42 AM, Bhushan Bharat-R65777 wrote:
-----Original Message-----
From: kvm-ppc-owner@xxxxxxxxxxxxxxx
[mailto:kvm-ppc-owner@xxxxxxxxxxxxxxx] On Behalf Of Alexander Graf
Sent: Tuesday, May 15, 2012 8:01 PM
To: Bhushan Bharat-R65777
Cc: kvm-ppc@xxxxxxxxxxxxxxx; Bhushan Bharat-R65777
Subject: Re: [PATCH] KVM: PPC: Not optimizing MSR_CE and MSR_DE with
paravirt.
On 05/15/2012 09:37 AM, Bharat Bhushan wrote:
From: Bhushan Bharat-R65777<R65777@xxxxxxxxxxxxx>
If there is pending critical or machine check interrupt then guest
would like to capture it when guest enable MSR.CE and MSR_ME
respectively.
Also as mostly MSR_CE and MSR_ME are updated with rfi/rfci/rfmii
which anyway traps so removing the the paravirt optimization for
MSR.CE and MSR.ME.
It's only not safe for e500mc and above, right?
For e500mc and above the paravirt emulation code will not come into
picture, And critical and machine check interrupt will happen only if MSR
have corresponding bits set. So they are already safe. Is not it?
Yup, though it might be worth documenting the fact with a few #ifdef's,
in case anyone wants to run PR KVM on e500mc ever.
Synchronous error report machine checks don't depend on MSR[ME] in case of e500mc.
E500v2 and book3s should be
fine.
And with this patch e500v2 will be fine? Not sure of book3s :).
Well, e500v2 has edge triggered MCs, no? MSR.CE is unsafe however, as
criticals are basically the same as externals.
In case of e500v2 machine check would be reported if MSR[ME], but if MSR[ME] is not set
the core would enter a check stop state. Yes, machine checks on e500v2 are edge triggered.
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?
Alex
--
To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
