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[Xen-devel] [PATCH] Dom0 Kernel - Fixes for saving/restoring MSI/MSI-X across Dom0 S3

Hi, Keir,

This patch is a bugfix for saving and restoring MSI/MSI-X across S3. Currently, 
Dom0's PCI layer unmaps MSI when S3 and maps them back when resuming. However, 
this triggers unexpected behaviors. For example, if the drivers still holds 
that irq at the point of unmapping MSI, Xen will force unbind that pirq. But 
after resume, we have no mechanism to rebind that pirq. The device can not 
receive interrupt then.
With this patch, MSI/MSI-X capabilities and tables are saved in Dom0 when S3 
and restored when resume. Actually, this is also the approach that kernel 
takes. The only concern is that Dom0 should not touch MSI/MSI-X, they are owned 
by VMM itself. Maybe adding a hypercall to instruct Xen to do the 
saving/restoring is good. I wonder whether the reason is strong enough for 
adding a hypercall for such purpose.

So Keir, maybe you can tell what is your prefer?

Best Regards
Haitao Shan

Attachment: msi.patch
Description: msi.patch

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