Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753386AbbHMPLX (ORCPT ); Thu, 13 Aug 2015 11:11:23 -0400 Received: from foss.arm.com ([217.140.101.70]:35313 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753372AbbHMPLU (ORCPT ); Thu, 13 Aug 2015 11:11:20 -0400 Message-ID: <55CCB393.1040909@arm.com> Date: Thu, 13 Aug 2015 16:11:15 +0100 From: Marc Zyngier Organization: ARM Ltd User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.7.0 MIME-Version: 1.0 To: Robert Richter , Thomas Gleixner , Jason Cooper CC: Tirumalesh Chalamarla , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Robert Richter Subject: Re: [PATCH v2 3/5] irqchip, gicv3: Workaround for Cavium ThunderX erratum 23154 References: <1439477277-6157-1-git-send-email-rric@kernel.org> <1439477277-6157-4-git-send-email-rric@kernel.org> In-Reply-To: <1439477277-6157-4-git-send-email-rric@kernel.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3212 Lines: 101 On 13/08/15 15:47, Robert Richter wrote: > From: Robert Richter > > This patch implements Cavium ThunderX erratum 23154. > > The gicv3 of ThunderX requires a modified version for reading the IAR > status to ensure data synchronization. Since this is in the fast-path > and called with each interrupt, runtime patching is used using jump > label patching for smallest overhead (no-op). This is the same > technique as used for tracepoints. > > v2: > * implement code in a single asm() to keep instruction sequence > * added comment to the code that explains the erratum > * apply workaround also if running as guest, thus check MIDR > > Signed-off-by: Robert Richter > --- > drivers/irqchip/irq-gic-v3.c | 45 +++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 44 insertions(+), 1 deletion(-) > > diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c > index 1a91902be0b1..2f80a11621a0 100644 > --- a/drivers/irqchip/irq-gic-v3.c > +++ b/drivers/irqchip/irq-gic-v3.c > @@ -107,7 +107,7 @@ static void gic_redist_wait_for_rwp(void) > } > > /* Low level accessors */ > -static u64 __maybe_unused gic_read_iar(void) > +static u64 gic_read_iar_common(void) > { > u64 irqstat; > > @@ -115,6 +115,38 @@ static u64 __maybe_unused gic_read_iar(void) > return irqstat; > } > > +/* > + * Cavium ThunderX erratum 23154 > + * > + * The gicv3 of ThunderX requires a modified version for reading the > + * IAR status to ensure data synchronization (access to icc_iar1_el1 > + * is not sync'ed before and after). > + */ > +static u64 gic_read_iar_cavium_thunderx(void) > +{ > + u64 irqstat; > + > + asm volatile( > + "nop;nop;nop;nop\n\t" > + "nop;nop;nop;nop\n\t" > + "mrs_s %0, " __stringify(ICC_IAR1_EL1) "\n\t" > + "nop;nop;nop;nop" > + : "=r" (irqstat)); > + mb(); > + > + return irqstat; > +} > + > +struct static_key is_cavium_thunderx = STATIC_KEY_INIT_FALSE; > + > +static u64 __maybe_unused gic_read_iar(void) > +{ > + if (static_key_false(&is_cavium_thunderx)) > + return gic_read_iar_common(); > + else > + return gic_read_iar_cavium_thunderx(); > +} > + > static void __maybe_unused gic_write_pmr(u64 val) > { > asm volatile("msr_s " __stringify(ICC_PMR_EL1) ", %0" : : "r" (val)); > @@ -766,8 +798,19 @@ static const struct irq_domain_ops gic_irq_domain_ops = { > .free = gic_irq_domain_free, > }; > > +static void gicv3_enable_cavium_thunderx(void *data) > +{ > + static_key_slow_inc(&is_cavium_thunderx); > +} > + > static const struct gic_capabilities gicv3_errata[] = { > { > + .desc = "GIC: Cavium erratum 23154", > + .iidr = 0xa100034c, /* ThunderX pass 1.x */ > + .iidr_mask = 0xffff0fff, > + .init = gicv3_enable_cavium_thunderx, > + }, I'm even more puzzled. You're working around a CPU bug based on the ITS ID registers? Or have you swapped the detection methods for the two errata? M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/