On 01/10/2020 21:58, Sean Christopherson wrote: > On Thu, Oct 01, 2020 at 01:32:04PM -0700, Yu, Yu-cheng wrote: >> On 10/1/2020 10:43 AM, Andy Lutomirski wrote: >>> The question is: what do we do about it? We have two basic choices, I >>> think. >>> >>> a) Decide that the saved FPU for a task *must* be valid at all times. >>> If there's a failure to restore state, kill the task. >>> >>> b) Improve our failed restoration handling and maybe even >>> intentionally make it possible to create illegal state to allow >>> testing. >>> >>> (a) sounds like a nice concept, but I'm not convinced it's practical. >>> For example, I'm not even convinced that the set of valid SSP values >>> is documented. > Eh, crappy SDM writing isn't a good reason to make our lives harder. The > SSP MSRs are canonical MSRs and follow the same rules as the SYSCALL, > FS/GS BASE, etc... MSRs. I'll file an SDM bug.
Don't forget the added constraint of being 4 byte aligned. ;) But the SDM is fine in this regard, at least as far as Vol4 goes, even if does have an excessively verbose way of expressing itself. ~Andrew
