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From: Max Filippov <jcmvbkbc@gmail.com>
Date: Tue, 10 Jan 2017 10:45:06 -0800
Message-ID: <CAMo8Bf+sZ_5N_ozXkoq3+Kfi18RDnNAvBpZTg0tG5NyWQF_bkw@mail.gmail.com>
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Subject: Re: [Qemu-devel] implementing architectural timers using QEMU timers
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To: Frederic Konrad <fred.konrad@greensocs.com>
Cc: qemu-devel <qemu-devel@nongnu.org>, Pavel Dovgaluk <Pavel.Dovgaluk@ispras.ru>, Alex Bligh <alex@alex.org.uk>, Richard Henderson <rth@twiddle.net>

On Tue, Jan 10, 2017 at 1:10 AM, Frederic Konrad
<fred.konrad@greensocs.com> wrote:
> On 01/09/2017 04:18 PM, Max Filippov wrote:
>> I'm trying to reimplement xtensa CCOUNT (cycle counter) and
>> CCOMPARE (CCOUNT-based timer interrupts) using QEMU
>> timers. That is CCOUNT value is derived from the
>> QEMU_CLOCK_VIRTUAL clock and CCOMPARE interrupts are
>> generated from the QEMU_CLOCK_VIRTUAL timer callbacks.
>> The code is here:
>>   https://github.com/OSLL/qemu-xtensa/commits/xtensa-ccount
>>
>> I've got the following issues doing that:
>>
>> - I thought that could be improved in -icount mode, so I tried that.
>>   It is better with -icount, but it's still not 100% accurate. That is
>>   I was able to observe guest reading QEMU clock value that is
>>   past QEMU timer deadline before that timer callback was
>>   invoked.
>>
>>   That sounds like a bug to me, is it?
>
> Did you try "sleep" icount option?
>
> eg:
> -icount 1,sleep=off

That doesn't seem to change anything.

-- 
Thanks.
-- Max