[PATCH 1/3] powerpc/64s: Mask NIP before checking against SRR0

[Sachin Sant]

> On 21-Dec-2021, at 7:20 PM, Michael Ellerman <mpe at ellerman.id.au> wrote:
> 
> When CONFIG_PPC_RFI_SRR_DEBUG=y we check that NIP and SRR0 match when
> returning from interrupts. This can trigger falsely if NIP has either of
> its two low bits set via sigreturn or ptrace, while SRR0 has its low two
> bits masked in hardware.
> 
> As a quick fix make sure to mask the low bits before doing the check.
> 
> Fixes: 59dc5bfca0cb ("powerpc/64s: avoid reloading (H)SRR registers if they are still valid")
> Reported-by: Sachin Sant <sachinp at linux.vnet.ibm.com>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> ---

Tested this 3 patch series successfully (with and without PPC_RFI_SRR_DEBUG)
on Power9/Power10 LPAR as well as Power9 PowerNV. 

Tested-by: Sachin Sant <sachinp at linux.vnet.ibm.com>