On Fri, Jan 04, 2013 at 05:44:15PM +0000, Marc Zyngier wrote: > __hyp_stub_install duplicates quite a bit of safe_svcmode_maskall > by forcing the CPU back to SVC. This is unnecessary, as > safe_svcmode_maskall is called just after. > > Furthermore, the way we build SPSR_hyp is buggy as we fail to mask > the interrupts, leading to interesting behaviours on TC2 + UEFI. > > The fix is to simply remove this code and rely on safe_svcmode_maskall > to do the right thing. > > Cc: Dave Martin <dave.martin@xxxxxxxxxx> > Reported-by: Harry Liebel <harry.liebel@xxxxxxx> > Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> Although there is clearly a bug here, it looks like interrupts will promptly get masked afterwards due to save_svcmode_maskall. This would only fail if there is an interrupts asserted during this hazard ...? Anyway, There's certainly no sense in trying to drop down to SVC mode twice, so I agree that it is better to delegate that to the save_svcmode_maskall macro. Reviewed-by: Dave Martin <dave.martin@xxxxxxxxxx> Cheers ---Dave > --- > arch/arm/kernel/hyp-stub.S | 12 +++--------- > 1 file changed, 3 insertions(+), 9 deletions(-) > > diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S > index 65b2417..da7e19f 100644 > --- a/arch/arm/kernel/hyp-stub.S > +++ b/arch/arm/kernel/hyp-stub.S > @@ -120,7 +120,8 @@ ENTRY(__hyp_stub_install_secondary) > * Eventually, CPU-specific code might be needed -- assume not for now > * > * This code relies on the "eret" instruction to synchronize the > - * various coprocessor accesses. > + * various coprocessor accesses. This is done when we switch to SVC > + * (see safe_svcmode_maskall). > */ > @ Now install the hypervisor stub: > adr r7, __hyp_stub_vectors > @@ -155,14 +156,7 @@ THUMB( orr r7, #(1 << 30) ) @ HSCTLR.TE > 1: > #endif > > - bic r7, r4, #MODE_MASK > - orr r7, r7, #SVC_MODE > -THUMB( orr r7, r7, #PSR_T_BIT ) > - msr spsr_cxsf, r7 @ This is SPSR_hyp. > - > - __MSR_ELR_HYP(14) @ msr elr_hyp, lr > - __ERET @ return, switching to SVC mode > - @ The boot CPU mode is left in r4. > + bx lr @ The boot CPU mode is left in r4. > ENDPROC(__hyp_stub_install_secondary) > > __hyp_stub_do_trap: > -- > 1.8.1 > > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
