On Sun, 29 Dec 2019, trueriver wrote:

> > HT is turned off intentionally for security purposes. Some of the
> Intel CPU vulnerabilities demonstrated within the recent years depend on
> the side channels within the resources shared by the threads of the same
> physical core. Thus it's advisable to not enable it
> 
> Thanks for that explanation -  yes that's sensible. 
> 
> With the option set to allow HT, I'm now wondering if there is a Xen 
> setting to force Xen to allocate both virtual cores in the same physical 
> core together? 

I don't know but I wouldn't expect one to appear in an old xen.
Given R4.0 is 4.8 so if such feature is there, most likely that's not 
available until some future Qubes version.

> That would mean you'd always get an even number of virtual cores, they 
> would always be "core buddies", and this it's only that VMs own code 
> that can attempt those exploits. That would give almost the same level 
> of security but allow the extra performance.
> 
> Or am I missing some nasty potential exploit?



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