On 09/04/19 11:52, Igor Mammedov wrote: > it could be stolen RAM + black hole like TSEG, assuming fw can live without > RAM(0x30000+128K) range > (in this case fwcfg interface would only work for locking down the range) > > or > > we can actually have a dedicated SMRAM (like in my earlier RFC), > in this case FW can use RAM(0x30000+128K) when SMRAM isn't mapped into RAM > address space > (in this case fwcfg would be used to temporarily map SMRAM into normal RAM > and unmap/lock > after SMI relocation handler was initialized). > > If possible I'd prefer a simpler TSEG like variant.
I think TSEG-like behavior is between these two. That is, I believe we should have explicit open/close/lock operations. And, when the range is closed (meaning, closed+unlocked, or closed+locked), then the black hole should take effect for code that's not running in SMM. Put differently, its like the second choice, except the range never appears as normal RAM. "When SMRAM isn't mapped into RAM address space", then the address range shows "nothing" (black hole). Regarding "fw can live without RAM(0x30000+128K) range" -- do you mean whether the firmware could use another RAM area for fw_cfg DMA? If that's the question, then I wouldn't worry about it. I'd remove the 0x30000+128K range from the memory map, so the fw_cfg stuff (or anything else) would never allocate memory from the range. It's much more concerning to me however how the SMM infrastructure would deal with a hole in the memory map right there. Thanks Laszlo
