From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E7BD1C44501 for ; Thu, 9 Jul 2026 12:07:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=n/PnDXPcyoXfrg6ldJBfveqhHq0Ntq3HxAu5yHp4IaU=; b=Yosh/nNtlSxQVIb8j3I4C3RVvs GTKhCW5J0vWAZfmE/iu1wcLnt+2FhzZ2d7AnTbbzKcEqUgXFxPedGNFvcZg3ijD1KtSxq6OeQz7f8 C8CfEsbMA0zzHD3rcMj7p5DmvYDwrAe+FDdI3sdq2RbaxMhCe/OygtuFmZ7AMgcbzNt68cX6TY+Dj 5jBvxW3GH4BeFeX+yr0lMRlaPCs2L7Wy1XnzQ1hgEQUFbqyxSXebjsj1rXdfLXg3RwnIUPgjCLHvl 9zv77vQLnvPUaJp+RfOy3IlW+oAXh0FntnOH4nk1WS4ZfoP9s8/dzjbrh87W3/dZr3areP+U6woD6 SzOrjiVQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1whnWy-00000002JV5-2HQR; Thu, 09 Jul 2026 12:07:04 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1whnWw-00000002JUE-0uTp for linux-arm-kernel@lists.infradead.org; Thu, 09 Jul 2026 12:07:03 +0000 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 D264F3569; Thu, 9 Jul 2026 05:06:56 -0700 (PDT) Received: from [10.41.150.148] (e142021.arm.com [10.41.150.148]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 05E973F66F; Thu, 9 Jul 2026 05:06:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783598821; bh=jPtXJeS/69sVHJHwLW5PFf9uHtm+WegMDEkeOn5/+UY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=jwhKsbjBWbONaR3cbE8YYLNW83WLz7CITsLvHnWNTKklG84IrXtK14DRnZ1whfZhx cWi+Wg5k7sDU+z15Rm1DNs6WIN6c8gdhHNorK38niMOi0pr7VHopxOKO7bwwQfmgsv wsWsFIz989IDWMiUSTMHFD5ThS1olDSLQ2yFElPE= Message-ID: <00e8ba98-735d-4c78-9056-3032036183e7@arm.com> Date: Thu, 9 Jul 2026 14:06:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 14/15] arm_mpam: prevent MPAM-Fb accesses inside IRQ handler To: Ben Horgan , 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 , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20260702162229.4008659-1-andre.przywara@arm.com> <20260702162229.4008659-15-andre.przywara@arm.com> Content-Language: en-GB From: Andre Przywara In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260709_050702_354144_2ABB65FD X-CRM114-Status: GOOD ( 28.28 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On 7/3/26 12:54, Ben Horgan wrote: > Hi Andre, > > On 7/2/26 17:22, 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 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 MSC access. >> >> For simplicity just skip the ESR read when the MSC is not using direct >> MMIO accesses, and just ignore the pending interrupts. We will wrap up >> MPAM functionality regardless, knowing the exact error value will not >> change that. >> >> Signed-off-by: Andre Przywara >> --- >> drivers/resctrl/mpam_devices.c | 35 +++++++++++++++++++--------------- >> 1 file changed, 20 insertions(+), 15 deletions(-) >> >> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c >> index b858ff389bff..4a088e6cd235 100644 >> --- a/drivers/resctrl/mpam_devices.c >> +++ b/drivers/resctrl/mpam_devices.c >> @@ -2639,7 +2639,7 @@ static int mpam_disable_msc_ecr(void *_msc) >> >> static irqreturn_t __mpam_irq_handler(int irq, struct mpam_msc *msc) >> { >> - u64 reg; >> + u64 reg = 0; >> u16 partid; >> u8 errcode, pmg, ris; >> >> @@ -2648,25 +2648,30 @@ static irqreturn_t __mpam_irq_handler(int irq, struct mpam_msc *msc) >> &msc->accessibility))) >> return IRQ_NONE; >> >> - mpam_msc_read_esr(msc, ®); >> + /* MPAM-Fb MSC accesses cannot be done in atomic context. */ >> + if (msc->iface == MPAM_IFACE_MMIO) { >> + mpam_msc_read_esr(msc, ®); >> >> - errcode = FIELD_GET(MPAMF_ESR_ERRCODE, reg); >> - if (!errcode) >> - return IRQ_NONE; >> + errcode = FIELD_GET(MPAMF_ESR_ERRCODE, reg); >> + if (!errcode) >> + return IRQ_NONE; >> >> - /* Clear level triggered irq */ >> - mpam_msc_clear_esr(msc); >> + /* Clear level triggered irq */ >> + mpam_msc_clear_esr(msc); >> >> - partid = FIELD_GET(MPAMF_ESR_PARTID_MON, reg); >> - pmg = FIELD_GET(MPAMF_ESR_PMG, reg); >> - ris = FIELD_GET(MPAMF_ESR_RIS, reg); >> + partid = FIELD_GET(MPAMF_ESR_PARTID_MON, reg); >> + pmg = FIELD_GET(MPAMF_ESR_PMG, reg); >> + ris = FIELD_GET(MPAMF_ESR_RIS, reg); >> >> - pr_err_ratelimited("error irq from msc:%u '%s', partid:%u, pmg: %u, ris: %u\n", >> - msc->id, mpam_errcode_names[errcode], partid, pmg, >> - ris); >> + pr_err_ratelimited("error irq from msc:%u '%s', partid:%u, pmg: %u, ris: %u\n", >> + msc->id, mpam_errcode_names[errcode], partid, >> + pmg, ris); >> >> - /* Disable this interrupt. */ >> - mpam_disable_msc_ecr(msc); >> + /* Disable this interrupt. */ >> + mpam_disable_msc_ecr(msc); > > As an error interrupt is final can we just disable the IRQ? Doing that should be covered by mpam_unregister_irqs() as part of the mpam_broken_work, shouldn't it? Or do you want to do it earlier? > Is it > useful? I see there is a function disable_irq_no_sync(). If we want to do it earlier, the _nosync variant sounds promising, although the comment talks about it being nested, so I guess it would need to be balanced? Which might be tricky here, since I guess the IRQ would be disabled again in mpam_unregister_irqs()? >> + } else { >> + pr_err_ratelimited("unknown error irq from msc:%u\n", msc->id); > > Should we report by irq number? > As MSC may share interrupts we don't know which MSC caused the error irq > at this point. On MMIO platforms we read the ESR to establish this. I see what you mean, though I am not sure if the user would be able to make sense of any interrupt number? I would put it in anyway, more information doesn't hurt. Cheers, Andre > Thanks, > > Ben > >> + } >> >> /* Are we racing with the thread disabling MPAM? */ >> if (!mpam_is_enabled()) >