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Re: [Qemu-devel] [patch v5 11/12] vfio: device may stuck in D3 when doin

From: Chen Fan
Subject: Re: [Qemu-devel] [patch v5 11/12] vfio: device may stuck in D3 when doing aer recovery
Date: Fri, 25 Mar 2016 09:38:09 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0

On 03/25/2016 06:54 AM, Alex Williamson wrote:
On Wed, 23 Mar 2016 18:12:06 +0800
Cao jin <address@hidden> wrote:

From: Chen Fan <address@hidden>

when a physical device aer occurred, the device state probably
is not in D0 in a short time, if we recover the device quickly.
we may stuck in D3 state when force to change device state to D0.
we may need to wait for a short time to inject the error to guest.

Signed-off-by: Chen Fan <address@hidden>
  hw/vfio/pci.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
index 25fc095..5216e7f 100644
--- a/hw/vfio/pci.c
+++ b/hw/vfio/pci.c
@@ -2658,6 +2658,9 @@ static void vfio_err_notifier_handler(void *opaque)
          msg.severity = isfatal ? PCI_ERR_ROOT_CMD_FATAL_EN :
+ /* wait a bit to ensure aer device is ready */
+        usleep(2 * 1000);
Where does this number come from?  Why would the device be in D3?  I
don't understand this at all.
Hi Alex,

    when I tested the code in my environment, I found that when I used
the aer-inject module to inject a fake aer error to device on host, the qemu
would throw out the message "vfio: Unable to power on device, stuck in D3"
on and off. if I use "gdb" to debug the vfio_pci_pre_reset, the phenomenon
would not appearance, I just thought it should be some timing race issue,
so I use a sleep() to wait 2ms (double the reset time of 1ms) to ensure the
device state is ready. maybe the root reason still need to be investigated deeply.


          pcie_aer_msg(dev, &msg);


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