> -----Original Message----- > From: Alexander Graf [mailto:agraf@xxxxxxx] > Sent: Thursday, July 17, 2014 9:58 PM > To: Bhushan Bharat-R65777; kvm-ppc@xxxxxxxxxxxxxxx > Cc: kvm@xxxxxxxxxxxxxxx; Wood Scott-B07421; Yoder Stuart-B08248 > Subject: Re: [PATCH] kvm: ppc: booke: Restore SPRG3 when entering guest > > > On 17.07.14 18:24, Bharat.Bhushan@xxxxxxxxxxxxx wrote: > > > >> -----Original Message----- > >> From: Alexander Graf [mailto:agraf@xxxxxxx] > >> Sent: Thursday, July 17, 2014 9:41 PM > >> To: Bhushan Bharat-R65777; kvm-ppc@xxxxxxxxxxxxxxx > >> Cc: kvm@xxxxxxxxxxxxxxx; Wood Scott-B07421; Yoder Stuart-B08248 > >> Subject: Re: [PATCH] kvm: ppc: booke: Restore SPRG3 when entering > >> guest > >> > >> > >> On 16.07.14 08:02, Bharat Bhushan wrote: > >>> SPRG3 is guest accessible and SPRG3 can be clobbered by host or > >>> another guest, So this need to be restored when loading guest state. > >>> > >>> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@xxxxxxxxxxxxx> > >>> --- > >>> arch/powerpc/kvm/booke_interrupts.S | 2 ++ > >>> 1 file changed, 2 insertions(+) > >>> > >>> diff --git a/arch/powerpc/kvm/booke_interrupts.S > >>> b/arch/powerpc/kvm/booke_interrupts.S > >>> index 2c6deb5ef..0d3403f 100644 > >>> --- a/arch/powerpc/kvm/booke_interrupts.S > >>> +++ b/arch/powerpc/kvm/booke_interrupts.S > >>> @@ -459,6 +459,8 @@ lightweight_exit: > >>> * written directly to the shared area, so we > >>> * need to reload them here with the guest's values. > >>> */ > >>> + PPC_LD(r3, VCPU_SHARED_SPRG3, r5) > >>> + mtspr SPRN_SPRG3, r3 > >> We also need to restore it when resuming the host, no? > > I do not think host expect some meaningful value when returning from guest, > same true for SPRG4-7. > > So there seems no reason to save host values and restore them. > > Hmm - arch/powerpc/include/asm/reg.h says: > > * All 32-bit: > * - SPRG3 current thread_info pointer > * (virtual on BookE, physical on others) > > but I can indeed find no trace of usage anywhere. This at least needs to go into > the patch description. I will add a comment in code as well. Thanks -Bharat > > > Alex -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
