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Re: [Qemu-devel] [PATCH RFC] pci: call PCIDeviceClass->exit on its .real


From: Cao jin
Subject: Re: [Qemu-devel] [PATCH RFC] pci: call PCIDeviceClass->exit on its .realize failure
Date: Mon, 19 Sep 2016 14:16:54 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0

Hi,
    sorry for replying late(was in vacation).

On 09/14/2016 07:59 PM, Marcel Apfelbaum wrote:
On 09/14/2016 12:14 PM, Cao jin wrote:
It cannot guarantee all pci devices will free the allocated resource in
its .realize function on realize failure.

CC: Michael S. Tsirkin <address@hidden>
CC: Marcel Apfelbaum <address@hidden>
Signed-off-by: Cao jin <address@hidden>
---

I found not all the devices will free the allocated resources on .realize
failure, and .exit function is the one who take responsibility to free
all
the resource. In theory, I think it should be PCIDeviceClass->exit who
does
the cleanup on realize failure, with appropriate check whether certain
resources is allocated.
It passed make check, but maybe need more confirmation, so, RFC.



Hi,

I think the call to pc->exit is not necessary here.

The call to pc->realize failed, so it is the callee (pc)
responsibility to clean the resources.

Please see in the same method:

      pci_add_option_rom(pci_dev, is_default_rom, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
             pci_qdev_unrealize(DEVICE(pci_dev), NULL);

              ^^^^^^^^^^^^^^^^^^^

This time we call pci_qdev_unrealize (that will call pc->exit)
because pc->realize succeeded and it is now the caller responsibility
to clean the resources.


Have you found a specific scenario that causes problems?

No, it came to my mind when doing the patch "convert to error". Look usb_xhci_realize(), it will call usb_xhci_init to do some resource allocation, but won't free the resource once return because of msi_init's failure(that may be my fault), so the following patch[*] move it down.

I agree your view above. We can forget this patch:)

[*]http://lists.nongnu.org/archive/html/qemu-devel/2016-09/msg03063.html

--
Yours Sincerely,

Cao jin





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