On 02/07/18 15:57, Igor Mammedov wrote:
On Wed, 7 Feb 2018 08:51:58 -0500 Stefan Berger firstname.lastname@example.org wrote:
On 01/10/2018 08:22 AM, Laszlo Ersek wrote:
On 01/09/18 20:02, Stefan Berger wrote:
So the point is SMM is needed for UEFI. QEMU would need to provide the ACPI code for it, which is basically a translation of the ACPI from EDK2 so that this could work. To support SeaBIOS as well, we would have to be able to distinguish a BIOS from the UEFI on the QEMU level so that we could produce different ACPI (no SMI and different OperationRegion than 0xFFFF 0000 for SeaBIOS), *if* on a system with a BIOS the memory area can be considered to be safe (like that EDK2 variable).
Does KVM actually restrict access to SMM memory (implements SMRR MSRs)?
KVM does not implement SMRRs, but QEMU+KVM implement SMRAM. OVMF exposes the Q35 TSEG region as SMRAM to the edk2 machinery. TSEG is controlled through various chipset registers.
Paolo's presentation and slides from 2015:
And even with SMRR, memory might be exposed to another cpu on cpu hotplug in current hotplug impl. if malicious code wins SIPI race in bringing up hotplugged CPU from (unprotected) reset state.
Yes, VCPU hotplug isn't even expected to work with SMM at the moment. "Don't do that just yet."