From: Peter Maydell <peter.maydell@linaro.org>
To: QEMU Developers <qemu-devel@nongnu.org>
Cc: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
"KONRAD Frederic" <frederic.konrad@adacore.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Mark Cave-Ayland" <mark.cave-ayland@ilande.co.uk>,
"Fabien Chouteau" <chouteau@adacore.com>
Subject: Re: [PATCH v2 0/3] Convert sparc devices to new ptimer API
Date: Thu, 24 Oct 2019 13:19:08 +0100 [thread overview]
Message-ID: <CAFEAcA8d6xXp+bCJCSWwD47Omfrenh4C=4NC3cFm4pEAHhkGmQ@mail.gmail.com> (raw)
In-Reply-To: <20191021134357.14266-1-peter.maydell@linaro.org>
On Mon, 21 Oct 2019 at 14:43, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> This patchset converts the devices used by sparc machines to the new
> ptimer API.
>
> Currently the ptimer design uses a QEMU bottom-half as its mechanism
> for calling back into the device model using the ptimer when the
> timer has expired. Unfortunately this design is fatally flawed,
> because it means that there is a lag between the ptimer updating its
> own state and the device callback function updating device state, and
> guest accesses to device registers between the two can return
> inconsistent device state. This was reported as a bug in a specific
> timer device but it's a problem with the generic ptimer code:
> https://bugs.launchpad.net/qemu/+bug/1777777
>
> The updates to the individual ptimer devices are straightforward:
> we need to add begin/commit calls around the various places that
> modify the ptimer state, and use the new ptimer_init() function
> to create the timer.
>
> Changes v1->v2:
> * patches 2 and 3 are the old 1 and 2 and have been reviewed
> * patch 1 is new and removes a pointless NULL check; without
> this we'd probably have got Coverity errors when patch 3
> added a use of t->timer before the check for it being NULL
I'm going to apply these to target-arm.next; I know they haven't
been on list long but the change since v1 is only minor and
they've all been reviewed.
thanks
-- PMM
next prev parent reply other threads:[~2019-10-24 13:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-21 13:43 [PATCH v2 0/3] Convert sparc devices to new ptimer API Peter Maydell
2019-10-21 13:43 ` [PATCH v2 1/3] hw/timer/slavio_timer: Remove useless check for NULL t->timer Peter Maydell
2019-10-21 14:03 ` Philippe Mathieu-Daudé
2019-10-21 16:24 ` Richard Henderson
2019-10-21 13:43 ` [PATCH v2 2/3] hw/timer/grlib_gptimer.c: Switch to transaction-based ptimer API Peter Maydell
2019-10-21 13:43 ` [PATCH v2 3/3] hw/timer/slavio_timer.c: " Peter Maydell
2019-10-21 14:06 ` [PATCH v2 0/3] Convert sparc devices to new " Philippe Mathieu-Daudé
2019-10-24 12:19 ` Peter Maydell [this message]
2019-10-24 18:04 ` Mark Cave-Ayland
2019-10-24 18:17 ` Philippe Mathieu-Daudé
2019-10-25 7:32 ` Peter Maydell
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