From: Anthony Liguori <aliguori@us.ibm.com>
To: Eric B Munson <emunson@mgebm.net>
Cc: avi@redhat.com, mingo@redhat.com, x86@kernel.org, hpa@zytor.com,
arnd@arndb.de, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-arch@vger.kernel.org, ryanh@linux.vnet.ibm.com
Subject: Re: [PATCH 6/6 V2] Add age out of guest paused flag
Date: Tue, 01 Nov 2011 14:58:23 -0500 [thread overview]
Message-ID: <4EB04F5F.4010709@us.ibm.com> (raw)
In-Reply-To: <20111101195111.GA9852@mgebm.net>
On 11/01/2011 02:51 PM, Eric B Munson wrote:
> On Tue, 01 Nov 2011, Anthony Liguori wrote:
>
>> On 10/31/2011 03:07 PM, Eric B Munson wrote:
>>> The KVM_GUEST_PAUSED flag will prevent a guest from compaining about a soft
>>> lockup but it can mask real soft lockups if the flag isn't cleared when it is
>>> no longer relevant. This patch adds a kvm ioctl that the hypervisor will use
>>> when it resumes a guest to start a timer for aging out the flag. The time out
>>> will be specified by the hypervisor in the ioctl call.
>>>
>>> Signed-off-by: Eric B Munson<emunson@mgebm.net>
>>
>> Why not have the guest clear the flag when it acknowledges it?
>>
>> The hypervisor would unconditionally set the bit, and the guest
>> would do a testandclear to check if the bit is set. I think that
>> avoids the whole aging business.
>>
>> Regards,
>>
>> Anthony Liguori
>
> If you have a look at patch 5 of this series, the flag is cleared when the
> guest checks the validity of a soft lockup. However, the aging is meant to
> cover the case where the guest never sees a soft lockup. We don't want this
> flag to be stored for ever and end up delaying real soft lockup messages. With
> that case in mind, I thought this was a good/simple compramise.
If the guest clears the flag, then I don't think you have to worry about this.
Regards,
Anthony Liguori
next prev parent reply other threads:[~2011-11-01 19:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-31 20:07 [PATCH 0/6 V2] Avoid soft lockup message when KVM is stopped by host Eric B Munson
2011-10-31 20:07 ` [PATCH 1/6 V2] Add flag to indicate that a vm was stopped by the host Eric B Munson
2011-11-01 19:22 ` Anthony Liguori
2011-10-31 20:07 ` [PATCH 2/6 V2] Add functions to check if the host has stopped the vm Eric B Munson
2011-11-01 19:28 ` Anthony Liguori
2011-11-01 20:07 ` Eric B Munson
2011-10-31 20:07 ` [PATCH 3/6 V2] Add ioctl for KVM_GUEST_STOPPED Eric B Munson
2011-11-01 19:32 ` Anthony Liguori
2011-11-01 20:11 ` Eric B Munson
2011-10-31 20:07 ` [PATCH 4/6 V2] Add generic stubs for kvm stop check functions Eric B Munson
2011-10-31 20:07 ` [PATCH 5/6 V2] Add check for suspended vm in softlockup detector Eric B Munson
2011-10-31 20:07 ` [PATCH 6/6 V2] Add age out of guest paused flag Eric B Munson
2011-11-01 19:34 ` Anthony Liguori
2011-11-01 19:51 ` Eric B Munson
2011-11-01 19:58 ` Anthony Liguori [this message]
2011-11-01 20:10 ` Eric B Munson
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