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KVM: PPC: Book3S HV: Ensure radix guest has no SLB entries 

Commit 68ad28a4cd ("KVM: PPC: Book3S HV: Fix radix guest SLB side
channel") changed the older guest entry path, with the side effect
that vcpu->arch.slb_max no longer gets cleared for a radix guest.
This means that a HPT guest which loads some SLB entries, switches to
radix mode, runs the guest using the old guest entry path (e.g.,
because the indep_threads_mode module parameter has been set to
false), and then switches back to HPT mode would now see the old SLB
entries being present, whereas previously it would have seen no SLB
entries.

To avoid changing guest-visible behaviour, this adds a store
instruction to clear vcpu->arch.slb_max for a radix guest using the
old guest entry path.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This commit is contained in:
Paul Mackerras 2021-02-11 17:09:45 +11:00
parent a722076e94
commit ab950e1acd
1 changed files with 5 additions and 1 deletions
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6
arch/powerpc/kvm/book3s_hv_rmhandlers.S
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@ -1539,8 +1539,12 @@ guest_exit_cont: /* r9 = vcpu, r12 = trap, r13 = paca */
.endr
b guest_bypass
0: /* Sanitise radix guest SLB, see guest_exit_short_path comment. */
0: /*
* Sanitise radix guest SLB, see guest_exit_short_path comment.
* We clear vcpu->arch.slb_max to match earlier behaviour.
*/
li r0,0
stw r0,VCPU_SLB_MAX(r9)
slbmte r0,r0
li r4,1
slbmte r0,r4