On Wed, 2016-09-28 at 09:37 +1000, Gavin Shan wrote: > > Yeah, it's safe to update it with memory decoding on. As the function call > flow I listed in the changelog (as below), nobody should access the IOV BAR > when pci_update_resource() is called. However, the PF's memory BARs might > be accessed that time and it's not safe to disable PF's memory decoding. The problem isn't so much whether anybody accesses the IOV BAR while it's updated but whether the IOV BAR will decode at all. IE. The BAR is updated in two steps, 32-bit each. That means that there is a window where it contains a "bogus" value. If that bogus value conflicts with another BAR (another BAR of the PF or another PF of the same device for example) then there is a risk of something bad happening if the driver accesses that conflicting resource during that window. On the other hand, if the IOV BAR doesn't decode at all while the update is done, which I think is the case as I believe SR-IOV isn't enabled during the update (please verify), then we are safe. Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
