Re: [Qemu-devel] [PATCH v7 3/4] piix_pci: optimize set irq path

[Stefan Weil <weil@mail.berlios.de>]

Am 01.04.2011 13:43, schrieb Isaku Yamahata:
> optimize irq routing in piix_pic.c which has been a TODO.
> So far piix3 tracks each pirq level and checks whether a given pic pins is
> asserted by seeing if each pirq is mapped into the pic pin.
> This is independent on irq routing, but data path is on slow path.
>
> Given that irq routing is rarely changed and asserting pic pins is on
> data path, the path that asserts pic pins should be optimized and
> chainging irq routing should be on slow path.
> The new behavior with this patch series is to use bitmap which is 
> addressed
> by pirq and pic pins with a given irq routing.
> When pirq is asserted, the bitmap is set and see if the pic pins is
> asserted by checking the bitmaps.
> When irq routing is changed, rebuild the bitmap and re-assert pic pins.
>
> test:
> - create VM with 4 e1000 nics in different pci slots
> (i.e. fn=0 for each e1000)
> Thus those e1000's INTA are connected to each PIRQ[A-D].
> - run linux as guest and saw each devices triggers interrupt
> by seeing /proc/interrupts. And then confirmed that each PIRQ[A-D]
> surely asserted interrupts.
> Because irq 10 and 11 are shared by 4 e1000's, it only one NIC is 
> activated
> with ifconfig ethN up/down when counting interrupts.
>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
> ---
> Changes v4 -> v5:
> - fix piix_set_irq_pic()
>
> Changes v3 -> v4:
> - replace irq_num with pirq or pci_intx
>
> Changes v1 -> v2:
> - some minor clean ups
> - commit log message
> ---
> hw/piix_pci.c | 101 
> +++++++++++++++++++++++++++++++++++++++++++++++---------
> 1 files changed, 84 insertions(+), 17 deletions(-)
>
> diff --git a/hw/piix_pci.c b/hw/piix_pci.c
> index 35e420c..7ffb821 100644
> --- a/hw/piix_pci.c
> +++ b/hw/piix_pci.c
...


Hi,

I got a regression report which was obviously caused by this commit:

$ git bisect bad
ab431c283e7055bcd6fb622f212bb29e84a6a134 is the first bad commit
commit ab431c283e7055bcd6fb622f212bb29e84a6a134
Author: Isaku Yamahata <yamahata@valinux.co.jp>
Date:   Fri Apr 1 20:43:23 2011 +0900

My test scenario:

i386-softmmu/qemu -L pc-bios -cdrom tinycore_3.5.1.iso -m 256 -boot d 
-net nic -net user -net dump

* Boot the default configuration (tinycore, or tinycore debug).
* Wait until X Windows is up.
* Check the size of qemu*.pcap. If it is only a few bytes, the test failed.
   Emulated networking then does not work, Tinycore does not get an IP 
address via DHCP.

The original report used tinycore_3.6.iso and the latest w32 binaries 
from qemu.weilnetz.de
with the same result. It also says that other Linux distributions show 
the same problem
(Fedora-14-i686-Live-Desktop.iso).

Regards
Stefan W.