gwj / at91sam9263 · Commits

  • Move CharDriverState code out of vl.c ...
    6f97dba0 
    The motivating goal behind this is to allow other tools to use the CharDriver
code.  This patch is pure code motion except for the Makefile changes and the
copyright/header in qemu-char.c.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



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  • Move some declarations around in the QEMU CharDriver code ...
    0e82f34d 
    The goal of this series is to move the CharDriverState code out of vl.c and
into its own file, qemu-char.c.  This patch moves around some declarations so
the next patch can be pure code motion.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



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  • Increase default IO timeout from 10ms to 5s ...
    0a1af395 
    With the recent changes to the main loop, we no longer have unconditional
polling.  This means we can now sleep in select() for much longer than we
previously did.  This patch increases our select() sleep time from 10ms to 5s
which is effectively unlimited since we're going to wake up sooner than that
in almost all circumstances.

With this patch, I see the number of wake-ups with an idle dynamic ticks guest
drop from 80 per second to about 15 times per second.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



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  • Main loop fixes/cleanup ...
    56f3a5d0 
    Tidy up win32 main loop bits, allow timeout >= 1s, and force timeout to 0 if
there is a pending bottom half.



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  • Clarify qemu_bh_schedule_idle() usage ...
    80d3580b 
    Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



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  • Implement "info chardev" command. (Gerd Hoffmann) ...
    5ccfae10 
    This patch makes qemu keep track of the character devices in use and
implements a "info chardev" monitor command to print a list.

qemu_chr_open() sticks the devices into a linked list now.  It got a new
argument (label), so there is a name for each device.  It also assigns a
filename to each character device.  By default it just copyes the
filename passed in.  Individual drivers can fill in something else
though.  qemu_chr_open_pty() sets the filename to name of the pseudo tty
allocated.

Output looks like this:

  (qemu) info chardev
  monitor: filename=unix:/tmp/run.sh-26827/monitor,server,nowait
  serial0: filename=unix:/tmp/run.sh-26827/console,server
  serial1: filename=pty:/dev/pts/5
  parallel0: filename=vc:640x480

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



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  • fix bdrv_aio_read API breakage in qcow2 (Andrea Arcangeli) ...
    1490791f 
    I noticed the qemu_aio_flush was doing nothing at all. And a flood of
cmd_writeb commands leading to a noop-invocation of qemu_aio_flush
were executed.

In short all 'memset;goto redo' places must be fixed to use the bh and
not to call the callback in the context of bdrv_aio_read or the
bdrv_aio_read model falls apart. Reading from qcow2 holes is possible
with phyisical readahead (kind of breada in linux buffer cache).

This is needed at least for scsi, ide is lucky (or it has been
band-aided against this API breakage by fixing the symptom and not the
real bug).

Same bug exists in qcow of course, can be fixed later as it's less
urgent.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



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  • Make DMA bottom-half driven (v2) ...
    492c30af 
    The current DMA routines are driven by a call in main_loop_wait() after every
select.

This patch converts the DMA code to be driven by a constantly rescheduled
bottom half.  The advantage of using a scheduled bottom half is that we can
stop scheduling the bottom half when there no DMA channels are runnable.  This
means we can potentially detect this case and sleep longer in the main loop.

The only two architectures implementing DMA_run() are cris and i386.  For cris,
I converted it to a simple repeating bottom half.  I've only compile tested
this as cris does not seem to work on a 64-bit host.  It should be functionally
identical to the previous implementation so I expect it to work.

For x86, I've made sure to only fire the DMA bottom half if there is a DMA
channel that is runnable.  The effect of this is that unless you're using sb16
or a floppy disk, the DMA bottom half never fires.

You probably should test this malc.  My own benchmarks actually show slight
improvement by it's possible the change in timing could affect your demos.

Since v1, I've changed the code to use a BH instead of a timer.  cris at least
seems to depend on faster than 10ms polling.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



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  • Make bottom halves more robust ...
    1b435b10 
    Bottom halves are supposed to not complete until the next iteration of the main
loop.  This is very important to ensure that guests can not cause stack
overflows in the block driver code.  Right now, if you attempt to schedule a
bottom half within a bottom half callback, you will enter an infinite loop.

This patch uses the same logic that we use for the IOHandler loop to make the
bottom half processing robust in list manipulation while in a callback.

This patch also introduces idle scheduling for bottom halves.  qemu_bh_poll()
returns an indication of whether any bottom halves were successfully executed.
qemu_aio_wait() uses this to immediately return if a bottom half was executed
instead of waiting for a completion notification.

qemu_bh_schedule_idle() works around this by not reporting the callback has
run in the qemu_bh_poll loop.  qemu_aio_wait() probably needs some refactoring
but that would require a larger code audit.  idle scheduling seems like a good
compromise.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>




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