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From: Jan Kiszka <jan.kiszka@web.de>
To: Avi Kivity <avi@redhat.com>
Cc: kvm <kvm@vger.kernel.org>, qemu-devel <qemu-devel@nongnu.org>
Subject: Re: qemu vs. kvm: When to flush the coalesced mmio buffer?
Date: Mon, 03 Jan 2011 13:34:12 +0100	[thread overview]
Message-ID: <4D21C244.10901@web.de> (raw)
In-Reply-To: <4D21C1D0.6060301@redhat.com>

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Am 03.01.2011 13:32, Avi Kivity wrote:
> On 01/03/2011 02:11 PM, Jan Kiszka wrote:
>> Hi again,
>>
>> another subtle difference between qemu-kvm and upstream:
>>
>> When we leave the guest for an IO window (KVM_RUN returns EINTR or
>> EAGAIN), we call kvm_flush_coalesced_mmio_buffer in qemu-kvm but not in
>> upstream. When version is better? I can't find any rationales in both
>> git logs.
> 
> We must flush on EINTR, otherwise a live migration can leave some mmios
> in the source host and not replay them on the destination host.
> 
> (plus, as Gleb says, if you're in userspace you might as well flush)
> 

OK, will append a fix to my series.

Thanks,
Jan


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WARNING: multiple messages have this Message-ID (diff)
From: Jan Kiszka <jan.kiszka@web.de>
To: Avi Kivity <avi@redhat.com>
Cc: qemu-devel <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>
Subject: [Qemu-devel] Re: qemu vs. kvm: When to flush the coalesced mmio buffer?
Date: Mon, 03 Jan 2011 13:34:12 +0100	[thread overview]
Message-ID: <4D21C244.10901@web.de> (raw)
In-Reply-To: <4D21C1D0.6060301@redhat.com>

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Am 03.01.2011 13:32, Avi Kivity wrote:
> On 01/03/2011 02:11 PM, Jan Kiszka wrote:
>> Hi again,
>>
>> another subtle difference between qemu-kvm and upstream:
>>
>> When we leave the guest for an IO window (KVM_RUN returns EINTR or
>> EAGAIN), we call kvm_flush_coalesced_mmio_buffer in qemu-kvm but not in
>> upstream. When version is better? I can't find any rationales in both
>> git logs.
> 
> We must flush on EINTR, otherwise a live migration can leave some mmios
> in the source host and not replay them on the destination host.
> 
> (plus, as Gleb says, if you're in userspace you might as well flush)
> 

OK, will append a fix to my series.

Thanks,
Jan


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  reply	other threads:[~2011-01-03 12:34 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-03 12:11 qemu vs. kvm: When to flush the coalesced mmio buffer? Jan Kiszka
2011-01-03 12:11 ` [Qemu-devel] " Jan Kiszka
2011-01-03 12:25 ` Gleb Natapov
2011-01-03 12:25   ` Gleb Natapov
2011-01-03 12:32 ` Avi Kivity
2011-01-03 12:32   ` [Qemu-devel] " Avi Kivity
2011-01-03 12:34   ` Jan Kiszka [this message]
2011-01-03 12:34     ` Jan Kiszka

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