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Michael Brown 236299baa3 [xhci] Avoid DMA during shutdown if firmware has disabled bus mastering 
On some systems (observed with the Thunderbolt ports on a ThinkPad X1
Extreme Gen3 and a ThinkPad P53), the system firmware will disable bus
mastering on the xHCI controller and all PCI bridges at the point that
ExitBootServices() is called if the IOMMU is enabled.  This leaves the
xHCI controller unable to shut down cleanly since all commands will
fail with a timeout.

Commit 85eb961 ("[xhci] Allow for permanent failure of the command
mechanism") allows us to detect that this has happened and respond
cleanly.  However, some unidentified hardware component (either the
xHCI controller or one of the PCI bridges) seems to manage to enqueue
the attempted DMA operation and eventually complete it after the
operating system kernel has reenabled bus mastering.  This results in
a DMA operation to an area of memory that the hardware is no longer
permitted to access.  On Windows with the Driver Verifier enabled,
this will result in a STOP 0xE6 (DRIVER_VERIFIER_DMA_VIOLATION).

Work around this problem by detecting when bus mastering has been
disabled, and immediately failing the device to avoid initiating any
further DMA attempts.

Reported-by: Andreas Hammarskjöld <junior@2PintSoftware.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
 		2021-11-12 22:27:25 +00:00
.github/workflows [linux] Use host glibc system call wrappers 2021-02-28 23:28:23 +00:00
contrib [cloud] Allow multiple images to be imported simultaneously 2021-05-02 12:38:03 +01:00
src [xhci] Avoid DMA during shutdown if firmware has disabled bus mastering 2021-11-12 22:27:25 +00:00
COPYING [legal] Update GPLv2 licence text 2015-02-26 17:59:53 +00:00
COPYING.GPLv2 [legal] Update GPLv2 licence text 2015-02-26 17:59:53 +00:00
COPYING.UBDL [legal] Add support for the Unmodified Binary Distribution Licence 2015-03-02 12:07:14 +00:00
README [doc] Re-add README file 2010-05-28 00:03:47 +01:00

README 

iPXE README File

Quick start guide:

   cd src
   make

For any more detailed instructions, see http://ipxe.org