From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave.martin@linaro.org (Dave Martin) Date: Mon, 7 Jan 2013 12:18:07 +0000 Subject: [PATCH 2/2] ARM: hyp: simplify __hyp_stub_install epilog In-Reply-To: <1357321455-9264-3-git-send-email-marc.zyngier@arm.com> References: <1357321455-9264-1-git-send-email-marc.zyngier@arm.com> <1357321455-9264-3-git-send-email-marc.zyngier@arm.com> Message-ID: <20130107121807.GA2050@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 > Reported-by: Harry Liebel > Signed-off-by: Marc Zyngier 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 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 > >