Michael Ellerman mpe@ellerman.id.au writes:
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 9581906b5ee9..65cb14b56f8d 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -330,22 +330,18 @@ _GLOBAL(enter_rtas) clrldi r4,r4,2 /* convert to realmode address */ mtlr r4
- li r0,0
- ori r0,r0,MSR_EE|MSR_SE|MSR_BE|MSR_RI
- andc r0,r6,r0
li r9,1rldicr r9,r9,MSR_SF_LG,(63-MSR_SF_LG)- ori r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI|MSR_LE
- andc r6,r0,r9
One advantage of the old method is it can adapt to new MSR bits being set by the kernel.
For example we used to use RTAS on powernv, and this code didn't need updating to cater to MSR_HV being set. We will probably never use RTAS on bare-metal again, so that's OK.
But your change might break secure virtual machines, because it clears MSR_S whereas the old code didn't. I think SVMs did use RTAS, but I don't know whether it matters if it's called with MSR_S set or not?
Not sure if anyone will remember, or has a working setup they can test. Maybe for now we just copy MSR_S from the kernel MSR the way the current code does.
Would the kernel even be able to change the bit? I think only urfid can clear MSR_S.