From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-x243.google.com (mail-pf0-x243.google.com [IPv6:2607:f8b0:400e:c00::243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3x4QYk53X0zDr9C for ; Sat, 8 Jul 2017 19:05:46 +1000 (AEST) Received: by mail-pf0-x243.google.com with SMTP id c24so7609911pfe.1 for ; Sat, 08 Jul 2017 02:05:46 -0700 (PDT) Date: Sat, 8 Jul 2017 19:05:26 +1000 From: Nicholas Piggin To: Gautham R Shenoy Cc: Michael Ellerman , Michael Neuling , Vaidyanathan Srinivasan , Shilpasri G Bhat , "Rafael J. Wysocki" , Akshay Adiga , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH 5/5] powernv:idle: Disable LOSE_FULL_CONTEXT states when stop-api fails. Message-ID: <20170708190526.44ea9ab9@roar.ozlabs.ibm.com> In-Reply-To: <20170707173710.GE8913@in.ibm.com> References: <1499272696-28751-1-git-send-email-ego@linux.vnet.ibm.com> <1499272696-28751-6-git-send-email-ego@linux.vnet.ibm.com> <20170707012916.215ed32a@roar.ozlabs.ibm.com> <20170707173710.GE8913@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Fri, 7 Jul 2017 23:07:10 +0530 Gautham R Shenoy wrote: > On Fri, Jul 07, 2017 at 01:29:16AM +1000, Nicholas Piggin wrote: > > On Wed, 5 Jul 2017 22:08:16 +0530 > > "Gautham R. Shenoy" wrote: > > > > > From: "Gautham R. Shenoy" > > > > > > Currently, we use the opal call opal_slw_set_reg() to inform the that > > > the Sleep-Winkle Engine (SLW) to restore the contents of some of the > > > Hypervisor state on wakeup from deep idle states that lose full > > > hypervisor context (characterized by the flag > > > OPAL_PM_LOSE_FULL_CONTEXT). > > > > > > However, the current code has a bug in that if opal_slw_set_reg() > > > fails, we don't disable the use of these deep states (winkle on > > > POWER8, stop4 onwards on POWER9). > > > > > > This patch fixes this bug by ensuring that if the the sleep winkle > > > engine is unable to restore the hypervisor states in > > > pnv_save_sprs_for_deep_states(), then we mark as invalid the states > > > which lose full context. > > > > > > As a side-effect, since supported_cpuidle_states in > > > pnv_probe_idle_states() consists of flags of only the valid states, > > > this patch will ensure that no other subsystem in the kernel can use > > > the states which lose full context on stop-api failures. > > > > Looks good. Is there something minimal we can do for stable here? > > > > Aside question, do we need to restore LPCR at all with the SLW engine? > > It gets set up again when by the idle wakeup code. > > > > > > And does POWER9 really need MSR and PSSCR restored by SLW? (going a bit > > off topic here, I'm just curious) > > MSR is needed to be restored so that we wakeup with the right > endianness and with the IR,DR disabled. And POWER8 does not require this? > PSSCR is set to a value so that in case of a special wakeup for a > deep-stop, the SLW can program the core to go back to the stop level > provided by the PSSCR value via the stop-api. It always restores to deepest stop? Is there any way to restore to the achieved stop level? Maybe there is no usefulness for that. Thanks, Nick