From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id ABE3F5695; Fri, 31 Jul 2026 13:33:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785504803; cv=none; b=AYqskukKx5eARcUUV1AlmOBcQ5nDuEOJbhZ7FQ/tDJD31o3XT20ZcpxZukynezP1JC7fUkzO5IcaRz2pN6exyrX77ryB20B/GGzFczInIrBGM3AprFc4X/3HArdytbfgUmv9xtNuj1CBBTtRrdt/JwwT+VbU+cV9svBxVKH8FkI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785504803; c=relaxed/simple; bh=Su2Q0vEK8ZDYhYpvfxPBORRIylsS9MVKYgKQH/+k5h4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=N1QlbEWZnrtW/tlaotIZjAo+q5Akc6xw+kwGv7HDlghYxTAMM6XDx0vodIGzb81TARzY4tBRaMnKkpjxC2XricZzRh9vU2fLoS172S8pFxS5XCowj77vJGZEr3CfzNW4IhctnGzWqol513HxoRb26Bx598M8IL5OE/c8pJNGrfo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=H6BqC0ar; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="H6BqC0ar" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DE89C204C; Fri, 31 Jul 2026 06:33:16 -0700 (PDT) Received: from [10.2.212.8] (e134344.arm.com [10.2.212.8]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 17D5E3F7B4; Fri, 31 Jul 2026 06:33:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785504800; bh=Su2Q0vEK8ZDYhYpvfxPBORRIylsS9MVKYgKQH/+k5h4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=H6BqC0ar6aExA+pO/+IEowd3nNJXiVsPhWxc5JJ4A/C0p4EoRha2jNW2GwVXw1ssY OGudSuqZT8LMtet8hTH0KbY40RCd46zhLxWhXLwsk+uYittan+J86wnZ/93zZ7zkx2 Cd6/adrMz038bOfBVfB0uDbv9SsiPQEJNEq0QCIE= Message-ID: <0b190985-3a71-43fb-9530-d6b50faf2e27@arm.com> Date: Fri, 31 Jul 2026 14:33:16 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Thunderbird Daily Subject: Re: [PATCH v6 09/10] arm_mpam: change MPAM-Fb error IRQ to use a threaded IRQ handler To: Andre Przywara , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Len Brown , James Morse , Reinette Chatre , Fenghua Yu Cc: Jonathan Cameron , Srivathsa L Rao , Ganapatrao Kulkarni , Trilok Soni , Srinivas Ramana , Niyas Sait , Lee Trager , Ritwick Sharma , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260730152539.2712312-1-andre.przywara@arm.com> <20260730152539.2712312-10-andre.przywara@arm.com> Content-Language: en-US From: Ben Horgan In-Reply-To: <20260730152539.2712312-10-andre.przywara@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Andre, On 7/30/26 16:25, Andre Przywara wrote: > When an MPAM MSC gets into an error condition, it can trigger an error > IRQ. We cannot really do much about those errors, but we at least query > and log the error, then disable MPAM functionality. > > This error report relies on reading the MSC's error status register > (ESR) in the current hard-IRQ handler, which is not possible for MPAM-Fb > based MSC accesses, since they involve mailbox routines that might sleep. > The same is true for clearing the interrupt at the source, which requires > an MSC access as well. > > When an MSC is using MPAM-Fb, change the error IRQ to use a threaded IRQ > handler, with an empty hard IRQ routine, and doing all the MSC accesses > (to access the status and disable the IRQ line) in the threaded part. > The change is minimal, we just check for the first MSC access error and > bail out early. MMIO based MSCs keep using a hard-IRQ handler, since > they must be at least non-migrate-able when doing MSC accesses, for the > CPU affinity check to work. > Also forbid per-CPU interrupts (PPIs) for MPAM-Fb, as we cannot use a > threaded IRQ here. > > Signed-off-by: Andre Przywara > --- > drivers/resctrl/mpam_devices.c | 64 ++++++++++++++++++++++++++-------- > 1 file changed, 49 insertions(+), 15 deletions(-) > > diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c > index daaf3cf48475..606ae4af2be9 100644 > --- a/drivers/resctrl/mpam_devices.c > +++ b/drivers/resctrl/mpam_devices.c > @@ -2660,24 +2660,38 @@ static int mpam_disable_msc_ecr(void *_msc) > return 0; > } > > +/* > + * This will run as the threaded IRQ handler part when using MPAM-Fb, but > + * as the sole hard-IRQ handler for MMIO based accesses. > + */ > static irqreturn_t __mpam_irq_handler(int irq, struct mpam_msc *msc) > { > u64 reg; > + int ret; > u16 partid; > u8 errcode, pmg, ris; > > - if (WARN_ON_ONCE(!msc) || > + if (WARN_ON_ONCE(!msc)) > + return IRQ_NONE; > + > + if (msc->iface == MPAM_IFACE_MMIO && > WARN_ON_ONCE(!cpumask_test_cpu(smp_processor_id(), > &msc->accessibility))) > return IRQ_NONE; > > - mpam_msc_read_esr(msc, ®); > + ret = mpam_msc_read_esr(msc, ®); > + if (ret) { > + pr_err_ratelimited("unknown error irq from msc:%u\n", msc->id); > + > + /* Try out best here ... */ > + goto out_disable; > + } > > errcode = FIELD_GET(MPAMF_ESR_ERRCODE, reg); > if (!errcode) > return IRQ_NONE; > > - /* Clear level triggered irq */ > + /* Clear level triggered irq. Ignore errors, we need to proceed. */ > mpam_msc_clear_esr(msc); > > partid = FIELD_GET(MPAMF_ESR_PARTID_MON, reg); > @@ -2688,19 +2702,19 @@ static irqreturn_t __mpam_irq_handler(int irq, struct mpam_msc *msc) > msc->id, mpam_errcode_names[errcode], partid, pmg, > ris); > > - /* Disable this interrupt. */ > +out_disable: > + /* Disable this interrupt. Ignore errors, we need to proceed anyway. */ > mpam_disable_msc_ecr(msc); If we fail to disable the interrupt then I don't think we can claim we handled it. Shouldn't we, after scheduling broken work, return IRQ_NONE? Thanks, Ben > > - /* Are we racing with the thread disabling MPAM? */ > - if (!mpam_is_enabled()) > - return IRQ_HANDLED; > - > /* > - * Schedule the teardown work. Don't use a threaded IRQ as we can't > - * unregister the interrupt from the threaded part of the handler. > + * Schedule the teardown work. We have to defer it as we can't > + * unregister the interrupt from the threaded part of a handler. > + * Check whether we are racing with the thread disabling MPAM. > */ > - mpam_disable_reason = "hardware error interrupt"; > - schedule_work(&mpam_broken_work); > + if (mpam_is_enabled()) { > + mpam_disable_reason = "hardware error interrupt"; > + schedule_work(&mpam_broken_work); > + } > > return IRQ_HANDLED; > } > @@ -2736,6 +2750,11 @@ static int mpam_register_irqs(void) > /* The MPAM spec says the interrupt can be SPI, PPI or LPI */ > /* We anticipate sharing the interrupt with other MSCs */ > if (irq_is_percpu(irq)) { > + if (msc->iface != MPAM_IFACE_MMIO) { > + dev_err(&msc->pdev->dev, > + "Only MMIO MSCs can use per-CPU interrupts\n"); > + return -EINVAL; > + } > err = request_percpu_irq(irq, &mpam_ppi_handler, > "mpam:msc:error", > msc->error_dev_id); > @@ -2747,9 +2766,24 @@ static int mpam_register_irqs(void) > &_enable_percpu_irq, &irq, > true); > } else { > - err = devm_request_irq(&msc->pdev->dev, irq, > - &mpam_spi_handler, IRQF_SHARED, > - "mpam:msc:error", msc); > + irq_handler_t hard, threaded; > + > + /* > + * MPAM-Fb needs a sleepable context for the MSC > + * accesses, whereas MMIO requires at least a > + * non-migrateable context for the processor ID check. > + */ > + if (msc->iface == MPAM_IFACE_MMIO) { > + hard = &mpam_spi_handler; > + threaded = NULL; > + } else { > + hard = NULL; > + threaded = &mpam_spi_handler; > + } > + err = devm_request_threaded_irq(&msc->pdev->dev, irq, > + hard, threaded, > + IRQF_SHARED | IRQF_ONESHOT, > + "mpam:msc:error", msc); > if (err) > return err; > }