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Re: [Qemu-devel] [PATCH v5 11/11] pci: Convert msi_init() to Error and f

From: Cao jin
Subject: Re: [Qemu-devel] [PATCH v5 11/11] pci: Convert msi_init() to Error and fix callers to check it
Date: Mon, 23 May 2016 20:51:36 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0

On 05/23/2016 06:06 PM, Marcel Apfelbaum wrote:
On 05/17/2016 01:08 PM, Cao jin wrote:

On 05/15/2016 09:41 PM, Marcel Apfelbaum wrote:

That is why I am not quite sure about this device, msi has a relation
with shpc.

 From its previous behaviour, it can be seen that it don`t treat 'on'
as 'auto'.(I am not sure why it is different with others)

Its previous behaviour treat msi_init`s failure as fatal, and lead to
device creation fail. According to Markus`s comments(if I understand
him right), this device has no non-msi variants.

Actually it has. The bridge needs msi for the SHPC controller, as you said.
If you look into shpc_interrupt_update function (hw/pci/shpc.c) you can
see it can fall
back to legacy interrupts.

The only complication here is that msi is needed only if shpc is present.
So maybe having msi=on/off/auto is OK.

msi=auto => if shpc not present or msi broken results in msi = off, else
msi = on
msi=on => fails if shpc present and msi broken
msi=off => use legacy interrupts if shpc is present

Basically the msi flag has no meaning if shpc not present.

Thanks for the hint, v6 is on the way:)

Yours Sincerely,

Cao jin

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