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Re: [PATCH 1/1] pcie: Do not set power state for some hot-plugged device
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From: |
Gerd Hoffmann |
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Subject: |
Re: [PATCH 1/1] pcie: Do not set power state for some hot-plugged devices |
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Date: |
Wed, 15 Dec 2021 07:05:13 +0100 |
On Tue, Dec 14, 2021 at 09:53:12PM +0000, Annie Li wrote:
> After the PCIe device is hot-plugged, the device's power state is
> initialized as ON. However, the device isn't powered on yet, i.e.
> the PCI_EXP_SYSCTL_PCC bit isn't set to PCI_EXP_SLTCTL_PWR_ON.
> Later on, its power state will set back to OFF due to the non
> PCI_EXP_SLTCTL_PWR_ON state. The device is invisible until
> PCI_EXP_SLTCTL_PWR_ON is set.
>
> This may be appropriate for general PCIe hot-plug cases. However,
> if the device is hot-plugged when the VM is in VM_STATE_PRELAUNCH
> state, especially the system disk device, the firmware will fail
> to find the system disk. As a result, the guest fails to boot.
Maybe we should just not set DeviceState->hotplugged = true for devices
added in VM_STATE_PRELAUNCH? It's not actual hotplug (i.e. device added
while the system is running) after all ...
There are lots of places checking DeviceState->hotplugged, and I suspect
we have similar issues elsewhere.
take care,
Gerd