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Received: from crackle.ozlabs.ibm.com (ppp121-45-219-3.bras1.cbr2.internode.on.net [121.45.219.3]) by mail.messagingengine.com (Postfix) with ESMTPA id 5C3BFE44DF; Wed, 20 Feb 2019 06:25:17 -0500 (EST) Message-ID: Subject: Re: [PATCH] powerpc/powernv/idle: Restore IAMR after idle From: Russell Currey To: Akshay Adiga , Michael Ellerman Date: Wed, 20 Feb 2019 22:25:15 +1100 In-Reply-To: <20190220071503.GA4708@aks.ibm> References: <20190206062837.26917-1-ruscur@russell.cc> <20190220071503.GA4708@aks.ibm> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, 2019-02-20 at 12:45 +0530, Akshay Adiga wrote: > On Wed, Feb 06, 2019 at 05:28:37PM +1100, Russell Currey wrote: > > Without restoring the IAMR after idle, execution prevention on > > POWER9 > > with Radix MMU is overwritten and the kernel can freely execute > > userspace without > > faulting. > > > > This is necessary when returning from any stop state that modifies > > user > > state, as well as hypervisor state. > > > > To test how this fails without this patch, load the lkdtm driver > > and > > do the following: > > > > echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT > > > > which won't fault, then boot the kernel with powersave=off, where > > it > > will fault. Applying this patch will fix this. > > > > Fixes: 3b10d0095a1e ("powerpc/mm/radix: Prevent kernel execution of > > user > > space") > > Cc: > > Signed-off-by: Russell Currey > > --- > > arch/powerpc/include/asm/cpuidle.h | 1 + > > arch/powerpc/kernel/asm-offsets.c | 1 + > > arch/powerpc/kernel/idle_book3s.S | 20 ++++++++++++++++++++ > > 3 files changed, 22 insertions(+) > > > > diff --git a/arch/powerpc/include/asm/cpuidle.h > > b/arch/powerpc/include/asm/cpuidle.h > > index 43e5f31fe64d..ad67dbe59498 100644 > > --- a/arch/powerpc/include/asm/cpuidle.h > > +++ b/arch/powerpc/include/asm/cpuidle.h > > @@ -77,6 +77,7 @@ struct stop_sprs { > > u64 mmcr1; > > u64 mmcr2; > > u64 mmcra; > > + u64 iamr; > > }; > > > > #define PNV_IDLE_NAME_LEN 16 > > diff --git a/arch/powerpc/kernel/asm-offsets.c > > b/arch/powerpc/kernel/asm-offsets.c > > index 9ffc72ded73a..10e0314c2b0d 100644 > > --- a/arch/powerpc/kernel/asm-offsets.c > > +++ b/arch/powerpc/kernel/asm-offsets.c > > @@ -774,6 +774,7 @@ int main(void) > > STOP_SPR(STOP_MMCR1, mmcr1); > > STOP_SPR(STOP_MMCR2, mmcr2); > > STOP_SPR(STOP_MMCRA, mmcra); > > + STOP_SPR(STOP_IAMR, iamr); > > #endif > > > > DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER); > > diff --git a/arch/powerpc/kernel/idle_book3s.S > > b/arch/powerpc/kernel/idle_book3s.S > > index 7f5ac2e8581b..bb4f552f6c7e 100644 > > --- a/arch/powerpc/kernel/idle_book3s.S > > +++ b/arch/powerpc/kernel/idle_book3s.S > > @@ -200,6 +200,12 @@ pnv_powersave_common: > > /* Continue saving state */ > > SAVE_GPR(2, r1) > > SAVE_NVGPRS(r1) > > + > > +BEGIN_FTR_SECTION > > + mfspr r5, SPRN_IAMR > > + std r5, STOP_IAMR(r13) > > +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) > > + > > Are we trying to add for both power8 and power9 ? > power9 would be CPU_FTR_ARCH_300. > If I recall correctly I had this at P9 only but for some reason I changed it - the reason is probably just that I had it confused for something else. Michael can you confirm this should be P9 only?