Good question. SMM relocation is required when new CPU hot plugged. When doing SMM relocation, we will save/restore the contents of 0x30000.
Jeff -----Original Message----- From: edk2-devel [mailto:[email protected]] On Behalf Of Paolo Bonzini Sent: Wednesday, November 04, 2015 5:14 PM To: Fan, Jeff; Laszlo Ersek; Kinney, Michael D Cc: [email protected] Subject: Re: [edk2] [Patch 3/3] UefiCpuPkg/CpuDxe: Place APs into protected mode when ExitBootService On 27/10/2015 03:12, Fan, Jeff wrote: > Yes. On physical hw, Aps will not response SMI if Aps received SMI in > WFSI state. But Aps will have one pending SMI and will enter into SMM > once Aps receive Startup IPI. Interesting... so if the BIOS doesn't do SMBASE relocation, an INIT-SMI-SIPI sequence will run code at 0x30000 in system management mode---thus letting the OS poke at SMRAM? Related to this, how is SMBASE relocation handled in the case where CPUs are hotplugged? Is there a race between any firmware code that does SMBASE relocation for the new code, and the OS which could overwrite the SMBASE relocation stub at address 0x30000? Paolo _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
