On 11.07.2012, at 02:34, Scott Wood wrote: > Unlike classic, we don't really need the MSR change to be atomic with the > branch. This eliminates a trap as a KVM guest (in the absence of > hardware hypervisor extensions), where mtmsr is paravirtualized but rfi > is not. For a virtualized guest without any paravirtualization, this > eliminates an additional two traps (SRR0/1). > > Signed-off-by: Scott Wood <scottw...@freescale.com> > --- > arch/powerpc/kernel/entry_32.S | 16 ++++++++++++++++ > 1 files changed, 16 insertions(+), 0 deletions(-) > > diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S > index ba3aeb4..6bb637c 100644 > --- a/arch/powerpc/kernel/entry_32.S > +++ b/arch/powerpc/kernel/entry_32.S > @@ -193,6 +193,9 @@ transfer_to_handler_cont: > lwz r11,0(r9) /* virtual address of handler */ > lwz r9,4(r9) /* where to go when done */ > #ifdef CONFIG_TRACE_IRQFLAGS > +#ifdef CONFIG_BOOKE > + mtmsr r10 > +#else > lis r12,reenable_mmu@h > ori r12,r12,reenable_mmu@l > mtspr SPRN_SRR0,r12 > @@ -201,6 +204,7 @@ transfer_to_handler_cont: > RFI > reenable_mmu: /* re-enable mmu so we can */ > mfmsr r10 > +#endif /* !CONFIG_BOOKE */ > lwz r12,_MSR(r1) > xor r10,r10,r12 > andi. r10,r10,MSR_EE /* Did EE change? */ > @@ -247,11 +251,23 @@ reenable_mmu: /* re-enable > mmu so we can */ > mtlr r9 > bctr /* jump to handler */ > #else /* CONFIG_TRACE_IRQFLAGS */ > +#ifdef CONFIG_BOOKE > + /* > + * We're not changing address space on Book E, and the extra rfi > + * can hurt when virtualized without hardware support -- whereas > + * mtmsr can be paravirtualized.
We can always paravirtualize RFI as well if it makes sense. Alex _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
