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Re: [Qemu-devel] [PATCH] monitor: Add force option support to pci_del co


From: Marcos Oviedo
Subject: Re: [Qemu-devel] [PATCH] monitor: Add force option support to pci_del command
Date: Wed, 9 Jun 2010 11:00:06 -0300



On Wed, Jun 9, 2010 at 4:38 AM, Gerd Hoffmann <address@hidden> wrote:
On 06/09/10 07:37, Marcos Oviedo wrote:
This adds a way to force the removal/unplug of previously added pci
devices when ACPI-based hotplug mechanism is not present.

Point being?

If your guest can't handle pci hotplug it is pretty useless to plug in hardware in the first place.

If your guest supports pci hotplug it will be quite upset if you zap the hardware without asking via ACPI.

This make sense when you mistakenly add a pci device on a -s -S scenario, like the scenario described on the following bug: https://bugs.launchpad.net/qemu/+bug/544367.

When ACPI-based hotplug support is present on the guest and we run pci_del with the force option, the hotplug events will still be generated to the guest and the guest still will trigger the EJx event, which will end by calling pciej_write() on qemu side. This function will do nothing on a -f and pci hotplug support scenario, as the pci device was previously removed by pci_del.

Thanks!

Marcos

 

cheers,
 Gerd



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