# Re: \[PATCH v1\] KVM: PPC: Book3S HV: Prevent POWER7/8 TLB flush flushing SLB

- From: Michael Ellerman \<hidden\>
- Date: 2021-11-25 09:35:58 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/11/9525255
- Thread: https://ratatoskr.run/linuxppc-dev/2021/11/9525149/t.md

```text
On Fri, 19 Nov 2021 13:16:27 +1000, Nicholas Piggin wrote:
> The POWER9 ERAT flush instruction is a SLBIA with IH=7, which is a
> reserved value on POWER7/8. On POWER8 this invalidates the SLB entries
> above index 0, similarly to SLBIA IH=0.
> 
> If the SLB entries are invalidated, and then the guest is bypassed, the
> host SLB does not get re-loaded, so the bolted entries above 0 will be
> lost. This can result in kernel stack access causing a SLB fault.
> 
> [...]

Applied to powerpc/fixes.

[1/1] KVM: PPC: Book3S HV: Prevent POWER7/8 TLB flush flushing SLB
      https://git.kernel.org/powerpc/c/cf0b0e3712f7af90006f8317ff27278094c2c128

cheers
```