From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1424316AbdEYP2X (ORCPT ); Thu, 25 May 2017 11:28:23 -0400 Received: from foss.arm.com ([217.140.101.70]:51216 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1424300AbdEYP2M (ORCPT ); Thu, 25 May 2017 11:28:12 -0400 Date: Thu, 25 May 2017 16:28:14 +0100 From: Will Deacon To: Wei Huang Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com Subject: Re: [PATCH 1/1] drivers/perf: arm_pmu_acpi: avoid perf IRQ init when guest PMU is off Message-ID: <20170525152814.GR2859@arm.com> References: <1495636601-14726-1-git-send-email-wei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1495636601-14726-1-git-send-email-wei@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Wei, On Wed, May 24, 2017 at 09:36:41AM -0500, Wei Huang wrote: > We saw perf IRQ init failures when running Linux kernel in an ACPI > guest without PMU (i.e. pmu=off). This is because perf IRQ is not > present when pmu=off, but arm_pmu_acpi still tries to register > or unregister GSI. This patch addresses the problem by checking > gicc->performance_interrupt. If it is 0, which is the value set > by qemu when pmu=off, we skip the IRQ register/unregister process. > > [ 4.069470] bc00: 0000000000040b00 ffff0000089db190 > [ 4.070267] [] enable_percpu_irq+0xdc/0xe4 > [ 4.071192] [] arm_perf_starting_cpu+0x108/0x10c > [ 4.072200] [] cpuhp_invoke_callback+0x14c/0x4ac > [ 4.073210] [] cpuhp_thread_fun+0xd4/0x11c > [ 4.074132] [] smpboot_thread_fn+0x1b4/0x1c4 > [ 4.075081] [] kthread+0x10c/0x138 > [ 4.075921] [] ret_from_fork+0x10/0x50 > [ 4.076947] genirq: Setting trigger mode 4 for irq 43 failed > (gic_set_type+0x0/0x74) > > Signed-off-by: Wei Huang > --- > drivers/perf/arm_pmu_acpi.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c > index 34c862f..d6bb75d 100644 > --- a/drivers/perf/arm_pmu_acpi.c > +++ b/drivers/perf/arm_pmu_acpi.c > @@ -29,6 +29,9 @@ static int arm_pmu_acpi_register_irq(int cpu) > return -EINVAL; > > gsi = gicc->performance_interrupt; > + if (!gsi) > + return 0; So a GSI of zero means we return an IRQ of zero, which correctly gets treated as "No ACPI PMU"... > if (gicc->flags & ACPI_MADT_PERFORMANCE_IRQ_MODE) > trigger = ACPI_EDGE_SENSITIVE; > else > @@ -58,7 +61,8 @@ static void arm_pmu_acpi_unregister_irq(int cpu) > return; > > gsi = gicc->performance_interrupt; > - acpi_unregister_gsi(gsi); > + if (gsi) > + acpi_unregister_gsi(gsi); ... but then I don't see how we can get here, so I'll drop this hunk. Will