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[Xen-devel] RE: set_msi_affinity() vs. pci_restore_msi_state()

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: [Xen-devel] RE: set_msi_affinity() vs. pci_restore_msi_state()
From: "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>
Date: Mon, 8 Mar 2010 10:14:04 +0800
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Thread-topic: set_msi_affinity() vs. pci_restore_msi_state()
    Have you met any issue ?  Per my understanding, there is no problem here.  
For set_msi_affinity, it calls write_msi_msg to write the MSI info to real 
hardware and also update it to (msi_desc)entry->msg, so entry->msg should store 
the latest msi's data/addr. And only if pci_restore_msi_state uses entry->msg 
to restore msi state, the correct info should be restored. And the key point is 
that write_msi_msg not only update hardware's msi state, but it stores the 
latest MSI info to msi descriptor entry->msg.  

-----Original Message-----
From: Jan Beulich [mailto:JBeulich@xxxxxxxxxx] 
Sent: Saturday, March 06, 2010 12:04 AM
To: Zhang, Xiantao
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: set_msi_affinity() vs. pci_restore_msi_state()

Isn't the fact that the former updates the MSI message data without
updating the copy of it in memory a problem for the latter, i.e. won't
the latter restore stale information? While the problem (if there is one)
existed before c/s 20073, the fact that the vector now can change
seems to make the potential effect of this much worse.

Thanks, Jan

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