Signed-off-by: Stefan Tauner stefan.tauner@student.tuwien.ac.at --- Documentation/mysteries_intel.txt | 81 ++++++++++++++++++++++++++++++++++++- 1 files changed, 80 insertions(+), 1 deletions(-)
diff --git a/Documentation/mysteries_intel.txt b/Documentation/mysteries_intel.txt index d6d3dfb..8a9a113 100644 --- a/Documentation/mysteries_intel.txt +++ b/Documentation/mysteries_intel.txt @@ -15,4 +15,83 @@ See also http://www.flashrom.org/pipermail/flashrom/2011-August/007606.html
= Unlocking the ME region = -TODO + If the ME region is locked by the FRAP register in descriptor mode, the host + software is not allowed to read or write any address inside that region. There + are different ways to unlock access: + + - a pin strap: Flash Descriptor Security Override Strap (as indicated by the + Flash Descriptor Override Pin Strap Status (FDOPSS) in HSFS. That pin is + probably not accessible to end users on consumer boards (every Intel doc i + have seen stresses that this is for debugging in manufacturing only and + should not be available for end users). + The ME indicates this in bits [19:16] (Operation Mode) in the HFS register of + the HECI/MEI PCI device by setting them to 4 (SECOVR_JMPR) [MODE_CTRL]. + + - Intel Management Engine BIOS Extension (MEBx) Disable This option may be + available to end users on some boards usually accessible by hitting + ctrl+p after BIOS POST. Quote: "“Disabling” the Intel ME does not really + disable it: it causes the Intel ME code to be halted at an early stage of + the Intel ME’s booting so that the system has no traffic originating from + the Intel ME on any of the buses." [MEBX] + The ME indicates this in bits [19:16] (Operation Mode) in the HFS register of + the HECI/MEI PCI device by setting them to 3 (Soft Temporary Disable) + [MODE_CTRL]. + + - Previous to Ibex Peak/5 Series chipsets removing the DIMM from slot (or + channel?) #0 disables the ME completely, which may give the host access to + the ME region. + + - HMRFPO (Host ME Region Flash Protection Override) Enable MEI command + This is the most interesting one because it allows to temporarily disable + the ME region protection by software. The ME indicates this in bits [19:16] + (Operation Mode) in the HFS register of the HECI/MEI PCI device by setting + them to 5 (SECOVER_MEI_MSG) [MODE_CTRL]. + +== MEI/HECI == + Communication between the host software and the different services provided by + the ME is done via a packet-based protocol that uses MMIO transfers to one or + more virtual PCI devices. Upon this layer there exist various services that can + be used to read out hardware management values (e.g. temperatures, fan speeds + etc.). The lower levels of that protocol are well documented: + The locations/offsets of the PCI MMIO registers are noted in the chipset + datasheets. The actually communication is documented in a whitepaper [DCMI] and + an outdated as well as a current Linux kernel implementation (currently in + staging/ exist [KERNEL]. There exists a patch that re-implements this in user + space (as part of flashrom). + +== Problems == + The problem is that only very few higher level protocols are documented publicly, + especially the bunch of messages that contain the HMRFPO commands is probably + well protected and only documented in ME-specific docs and the BIOS writer's + guides. We are aware of a few leaked documents though that give us a few hints + about it, but nothing substantial regarding its implementation. + + The documents are somewhat contradicting each other in various points which + might be due to factual changes in process of time or due to the different + capabilities of the ME firmwares, example: + + Intel's Flash Programming Tool (FPT) "automatically stops ME writing to SPI + ME Region, to prevent both writing at the same time, causing data corruption." [ME8] + + "FPT is not HMRFPO-capable, so needs [the help of the FDOPS pin] HDA_SDO if + used to update the ME Region." [SPS] + + When looking at the various ME firmware editions (and different chipsets), things + get very unclear. Some docs say that HMRFPO needs to be sent before End-of-POST + (EOP), others say that the ME region can be updated in the field or that some + vendor tools use it for updates. This needs to be investigated further before + drawing any conclusion. + +[MODE_CTRL] Client Platform Enabling Tour: Platform Software + Document Number: 439167, Revision 1.2, page 52 +[MEBX] Intel® Management Engine BIOS Extension (MEBX) User’s Guide + Revision 1.2, Section 3.1 and 3.5 +[DCMI] DCMI Host Interface Specification + Revision 1.0 +[KERNEL] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=tree;f=dr... +[SPI_PROG] Ibex Peak SPI Programming Guide + Document Number: 403598, Revision 1.3, page 79 +[ME8] Manufacturing with Intel® Management Engine (ME) Firmware 8.X on Intel 7 Series + Revision 2.0, page 59 +[SPS] Manufacturing with Intel® Management Engine (ME) on Intel® C600 Series Chipset 1 for Romley Server 2 Platforms using Server Platform Services (SPS) Firmware + Revision 2.2, page 51
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Stefan Tauner