On Mon, Jul 31, 2023 at 12:45:19AM +0530, Vidya Sagar wrote: > PCIe 6.0, 6.12.1.1 specifies that downstream devices are permitted to > send upstream messages before they have been assigned a bus number and > such messages have a Requester ID with Bus number set to 00h. > If the Downstream port has ACS Source Validation enabled, these messages > will be detected as ACS violation error. > > Hence, disable ACS Source Validation in the bridge device during > hot-remove operation and re-enable it after enumeration of the > downstream hierarchy but before binding the respective device drivers. What are these messages that are sent before assignment of a bus number? What's the user-visible issue that occurs when they're blocked? Doesn't disabling Source Validation introduce a security hole because the device may spoof messages before Source Validation is re-enabled? PCIe r6.1 sec 6.12.1.1 does indeed point out that the downstream device is *permitted* to send these messages but the Implementation Note does *not* prescribe that Source Validation shall be disabled to let them through. It merely points out that the messages may be filtered if Source Validation is enabled. Thanks, Lukas
