Jan Kiszka wrote:
> If TXT is on and VT is locked but KVM sees tboot_enabled == 0, it
> won't check for FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX during setup
> and may consider VT unavailable.

If vt is locked, txt is on, tboot_enabled = 0, then it will check 
VMXON_OUTSIDE_SMX.
But at this point, if vt is on (still locked), the fn will return 0, which 
means vmx is not disabled by bios, correct?


> Moreover, if VT is not locked in that case, KVM will also not set
> FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX during hardware_enable,
> likely leaving VT off then, no? 

Sure, KVM will not set VMXON_INSIDE_SMX, but will set VMXON_OUTSIDE_SMX.
In that case, this means vt is on.

> 
> So my question is: Would it cause any harm to assume TXT being always
> on, even if it wasn't?

A bit confused.
Do you mean hardware TXT always on, i.e. set 
FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX = 1 always?
That's fine. No problem. No harm.
Or, do you mean set tboot_enabled = 1 always? if so, in case that the hardware 
TXT is disabled
(FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX = 0), then KVM will think vmx is 
disabled if feature msr is locked.

Shane--
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