[PATCH 2/4] KVM: PPC: Book3S HV: Fix radix guest SLB side channel

[Paul Mackerras]

On Mon, Jan 18, 2021 at 04:28:07PM +1000, Nicholas Piggin wrote:
> The slbmte instruction is legal in radix mode, including radix guest
> mode. This means radix guests can load the SLB with arbitrary data.
> 
> KVM host does not clear the SLB when exiting a guest if it was a
> radix guest, which would allow a rogue radix guest to use the SLB as
> a side channel to communicate with other guests.

No, because the code currently clears the SLB when entering a radix
guest, which you remove in the next patch.  I'm OK with moving the SLB
clearing from guest entry to guest exit, I guess, but I don't see that
you are in fact fixing anything by doing so.

Paul.