freebsd stable - Jul 2018 - Ryzen issues on FreeBSD ? (with sort of workaround)

On Thu, Jul 05, 2018 at 02:23:15PM +0100, Pete French
wrote:
> 
> 
> On 05/07/2018 11:47, Konstantin Belousov wrote:
> > Why do you state that they are saved/restored ?  What is the evidence
?
> 
> 
>
https://software.intel.com/en-us/blogs/2009/06/25/virtualization-and-performance-understanding-vm-exits
> 
> specificly...
> 
> 3) "Save MSRs in the VM-exit MSR-store area."
> 
> and
> 
> 5) "Load MSRs from the VM-exit MSR-load area."
> 
> but maybe thats not actyually true, I assumed it was given its an Intel 
> document, but admittedly its not an actual specification.
This is true, but absolutely irrelevant.

Modern CPUs have hundreds, if not thousands, MSR registers.  Only some of
them define architectural state, and saved/restored on the context switches.
Chicken bits are global knobs not relevant to the vmm entry.
> 
> 
> > On VM the patch should be NOP, testing it is a waste of time IMO.
> 
> 
> OK, will ignore that then. I am running the new patch on my workstation 
> now - I still need the old patch for the other files, yes ?
Which other files ?

> This is true, but absolutely irrelevant.
>
> Modern CPUs have hundreds, if not thousands, MSR registers.  Only some of
> them define architectural state, and saved/restored on the context
switches.
> Chicken bits are global knobs not relevant to the vmm entry.
That actually makes far more sense. I was kind of puzzled as to how it
would work if they were per VM :-)
> Which other files ?
sys/x86/include/specialreg.h and sys/x86/x86/cpu_machdep.c

Those are in your original patch as well as the change
to sys/amd64/amd64/initcpu.c, but your email earlier only
patches sys/amd64/amd64/initcpu.c and not the others.

So I assumed I would keep the changes to the other two files ?

-pete.