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From: Max Filippov <jcmvbkbc@gmail.com>
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>
Subject: Re: [Qemu-devel] implementing architectural timers using QEMU timers
Date: Tue, 10 Jan 2017 10:45:06 -0800	[thread overview]
Message-ID: <CAMo8Bf+sZ_5N_ozXkoq3+Kfi18RDnNAvBpZTg0tG5NyWQF_bkw@mail.gmail.com> (raw)
In-Reply-To: <cd817ab9-fd77-f52c-5ee7-7502b68959cb@greensocs.com>

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

      reply	other threads:[~2017-01-10 18:45 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-09 15:18 [Qemu-devel] implementing architectural timers using QEMU timers Max Filippov
2017-01-09 15:41 ` Alex Bligh
2017-01-10 15:22   ` Max Filippov
2017-01-10  8:31 ` Pavel Dovgalyuk
2017-01-10 18:39   ` Max Filippov
2017-01-10 18:47     ` Peter Maydell
2017-01-10 18:51       ` Max Filippov
2017-01-12 11:28     ` Pavel Dovgalyuk
2017-01-12 12:01       ` Peter Maydell
2017-01-12 12:19         ` Pavel Dovgalyuk
2017-01-16 17:19           ` Paolo Bonzini
2017-01-17  5:45             ` Pavel Dovgalyuk
2017-01-17 18:20             ` Max Filippov
2017-01-15 21:52       ` Max Filippov
2017-01-10  9:10 ` Frederic Konrad
2017-01-10 18:45   ` Max Filippov [this message]

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