Michael Ellerman <mpe@xxxxxxxxxxxxxx> 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 r9,1 >> - rldicr 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.
