On Sun, Oct 09, 2016 at 09:33:58PM +0300, Jarkko Sakkinen wrote: > > Sorry I missed this part. > > > > Here are the constraints for existing hardware: > > > > 1. All the existing CRB start only hardware has the iomem covering the > > control area and registers for multiple localities. > > 2. All the existing ACPI start hardware has only the control area. > > > > If you assume that SSDT does not have malicous behavior caused by either > > a BIOS bug or maybe a rootkit, then the current patch works for all the > > existing hardware. > > > > To counter-measure for unexpected behavior in non-existing hardware and > > buggy or malicious firmware it probably make sense to use crb_map_res to > > validate the part of the CRB registers that is not part of the control > > area.
I don't know how much I'd assume BIOS authors do what you think - the spec I saw for this seems very vauge. Certainly checking that locality region falls within the acpi mapping seems essential. > > Doing it in the way you proposed does not work for ACPI start devices. > > > > For them it should be done in the same way as I'm doing in the existing > > patch as for ACPI start devices the address below the control area are > > never accessed. Having a separate crb_map_res for CRB start only devices > > is sane thing to do for validation. > > Alternative is to do two structures crb_regs_head and crb_regs_tail, > which might be cleaner. I'm fine with going either route. Since the iomem doesn't actually exist for a configuration having two pointers is the better choice. Make sure one is null for the configuration that does not support it. The negative offset thing is way too subtle. Jason
