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[0/3] Convert ppc and microblaze devices to new ptimer API

Message ID 20191017132122.4402-1-peter.maydell@linaro.org
Headers show
Series Convert ppc and microblaze devices to new ptimer API | expand

Message

Peter Maydell Oct. 17, 2019, 1:21 p.m. UTC 
This patchset converts the devices used by ppc and microblaze
machines to the new ptimer API. (xilinx_timer is used by both,
hence putting both archs in the same patchset).

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.

Testing has been 'make check' only, which obviously doesn't
exercise the devices very much, so more specific testing would
be appreciated. I'm happy for these patches to go in via the
ppc tree if you want, or I can collect them up with the other
ptimer-related changes I'm sending for other archs.

thanks
--PMM

Peter Maydell (3):
  hw/net/fsl_etsec/etsec.c: Switch to transaction-based ptimer API
  hw/timer/xilinx_timer.c: Switch to transaction-based ptimer API
  hw/dma/xilinx_axidma.c: Switch to transaction-based ptimer API

 hw/net/fsl_etsec/etsec.h |  1 -
 hw/dma/xilinx_axidma.c   |  9 +++++----
 hw/net/fsl_etsec/etsec.c |  9 +++++----
 hw/timer/xilinx_timer.c  | 13 ++++++++-----
 4 files changed, 18 insertions(+), 14 deletions(-)

-- 
2.20.1

Comments

Peter Maydell Oct. 24, 2019, 12:16 p.m. UTC | #1 
On Thu, 17 Oct 2019 at 14:21, Peter Maydell <peter.maydell@linaro.org> wrote:
>

> This patchset converts the devices used by ppc and microblaze

> machines to the new ptimer API. (xilinx_timer is used by both,

> hence putting both archs in the same patchset).

>

> 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.

>

> Testing has been 'make check' only, which obviously doesn't

> exercise the devices very much, so more specific testing would

> be appreciated. I'm happy for these patches to go in via the

> ppc tree if you want, or I can collect them up with the other

> ptimer-related changes I'm sending for other archs.


I'll put these in via target-arm.next, since they've all
been reviewed now and nobody's suggested a preference
for some other route.

thanks
-- PMM