Re: [edk2-devel] CPU hotplug using SMM with QEMU+OVMF

Paolo Bonzini <pbonzini@...>

On 21/08/19 22:17, Kinney, Michael D wrote:

It makes sense to match real HW.
Note that it'd also be fine to match some kind of official Intel
specification even if no processor (currently?) supports it.

That puts us back to
the reset vector and handling the initial SMI at
3000:8000. That is all workable from a FW implementation
perspective. It look like the only issue left is DMA.

DMA protection of memory ranges is a chipset feature.
For the current QEMU implementation, what ranges of
memory are guaranteed to be protected from DMA? Is
it only A/B seg and TSEG?


Yes, all of these would work. Again, I'm interested in
having something that has a hope of being implemented in
real hardware.

Another, far easier to implement possibility could be a
lockable MSR (could be the existing
MSR_SMM_FEATURE_CONTROL) that allows programming the
SMBASE outside SMM. It would be nice if such a bit
could be defined by Intel.


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