Fabiano Rosas <faro...@linux.ibm.com> writes: > Michael Ellerman <m...@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 r9,1 >>> - 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.
Good point :) cheers
