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Re: [Qemu-devel] QEMU TB Unlinking due to interrupt.

From: Xin Tong
Subject: Re: [Qemu-devel] QEMU TB Unlinking due to interrupt.
Date: Fri, 9 Dec 2011 19:08:43 -0500

can you forward me the patch please. Peter. Also, as far as I
understand, tb unlinking can only happen in 2 cases.

1. some other tbs being invalidated.
2. interrrupt pending

Am I right ?



On Fri, Dec 9, 2011 at 6:45 PM, Peter Maydell <address@hidden> wrote:
> On 9 December 2011 18:44, Xin Tong <address@hidden> wrote:
>> Currently, QEMU unchains TBs if there is an interrupt pending. I would
>> like to know whether there is any reason behind this ? (why not
>> checking interrupt status in the beginning of every tb ?)
> The theory is that it's faster overall to do a slightly slow
> operation (tb unlinking) on interrupts rather than do a check
> at the beginning of every tb (happens a lot in the normal
> code path).
> However the tb unlinking code is racy and personally I think
> we should get rid of it in favour of a simpler scheme like a
> flag check. I have some prototype patches kicking around for
> this.
> -- PMM

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