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 F2A2030674E; Thu, 30 Jul 2026 12:47:27 +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=1785415650; cv=none; b=js6mGXAWt0cRAHmbJmCvCPT3A00f+6f7ge1ZcZmVesNCqKxSsoCrHbdPLMFZu04ZDlX0YJqtcdA6pLxEhrKB+2uCCM8Beoj7VNbkttFDeZvZRLxgGOacMbizhEv//wGjMrSD/3hzBF3MqYo3D0tGrMoYYSXFB0eX8kuQJ7UCFfM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785415650; c=relaxed/simple; bh=WfoefAgOES6CV8muplxagsKiTcKIhpvznQ3erz47QIs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cOYP8PkHnmKRrSvaaztpYIwckjNs/29N7EA0Vo2FFIGYcEo2eLHDz9K4BEzwVole9/UlMWO1xWyjrerc0WlVscwnprmK0/+0yi1gq0VDSk2PdhN7a/ZXzt8xZ0dHUT3lwMJ61P7NOaA229iZ7atgZCBt2Ma5rg8DJMzqU/NpogI= 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=M9GlJbEn; 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="M9GlJbEn" 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 CCBA91688; Thu, 30 Jul 2026 05:47:22 -0700 (PDT) Received: from [192.168.178.24] (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AFE693F86F; Thu, 30 Jul 2026 05:47:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785415646; bh=WfoefAgOES6CV8muplxagsKiTcKIhpvznQ3erz47QIs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=M9GlJbEnDyAE36ajxjU3N/JvgUuLPxebLwxy32c5OG18qrASRykhHyODOxg1C0mlQ 8fThFosPU3gph4odkmhtrOXhVxno4HzVAlL6/Ry9DXsKHWj48QmPZtNDRIisbzDaeX InQfqjrXh9dGRHgVaiju4ohl4n0GJWKae81oIRds= Message-ID: <3a06f20a-c7dd-4deb-abc5-b0f67faee343@arm.com> Date: Thu, 30 Jul 2026 14:47:22 +0200 Precedence: bulk X-Mailing-List: linux-acpi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 10/10] arm_mpam: detect and enable MPAM-Fb PCC support To: Lee Trager , Lorenzo Pieralisi , Hanjun Guo , Sudeep Holla , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Len Brown , James Morse , Ben Horgan , 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: <20260729134124.2506269-1-andre.przywara@arm.com> <20260729134124.2506269-11-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: 8bit Hi Lee, On 7/30/26 03:34, Lee Trager wrote: > On 7/29/26 6:41 AM, Andre Przywara wrote: > >> @@ -2231,7 +2316,7 @@ static void mpam_msc_drv_remove(struct >> platform_device *pdev) >>   static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device >> *pdev) >>   { >>       int err; >> -    u32 tmp; >> +    u32 pcc_subspace_id; >>       struct mpam_msc *msc; >>       struct resource *msc_res; >>       struct device *dev = &pdev->dev; >> @@ -2279,7 +2364,7 @@ static struct mpam_msc >> *do_mpam_msc_drv_probe(struct platform_device *pdev) >>       if (err) >>           return ERR_PTR(err); >> -    if (device_property_read_u32(&pdev->dev, "pcc-channel", &tmp)) >> +    if (device_property_read_u32(dev, "pcc-channel", &pcc_subspace_id)) >>           msc->iface = MPAM_IFACE_MMIO; >>       else >>           msc->iface = MPAM_IFACE_PCC; >> @@ -2295,6 +2380,36 @@ static struct mpam_msc >> *do_mpam_msc_drv_probe(struct platform_device *pdev) >>           } >>           msc->mapped_hwpage_sz = msc_res->end - msc_res->start; >>           msc->mapped_hwpage = io; >> +    } else if (msc->iface == MPAM_IFACE_PCC) { >> +        int ret; >> + >> +        msc->pcc_chan = mpam_pcc_chan_get(dev, pcc_subspace_id); >> +        if (IS_ERR(msc->pcc_chan)) { >> +            pr_err("Failed to request MSC PCC channel\n"); >> +            return ERR_CAST(msc->pcc_chan); >> +        } >> + >> +        if (msc->pcc_chan->pcc_chan->shmem_size < >> MPAM_FB_MAX_MSG_SIZE) { > > I think the PCC shared-memory size undercounts the required region. From > my understanding shmem_size is the length of the complete PCC shared- > memory region advertised by the PCCT and mapped by the PCC driver. > MPAM_FB_MAX_MSG_SIZE is the 4-byte protocol header stored in pcc_shmem- > >command + the 16-byte write payload. > > However, mpam_fb_build_write_message() places the payload after the > complete 16 byte struct acpi_pcct_ext_pcc_shared_memory. The largest > request therefore occupies 32 bytes of shared memory region(16-byte PCC > header+ 16-byte write payload). Thus a firmware region between 20 and 31 > bytes currently passes the check but overruns when constructing a write > request. I think this should be Ah, you are right, there are indeed multiple things at play here. > if (msc->pcc_chan->pcc_chan->shmem_size <> >     sizeof(struct acpi_pcct_ext_pcc_shared_memory) + >     MPAM_FB_MAX_MSG_SIZE - MPAM_FB_PROT_HEADER_LEN) I simplified that by just dropping MPAM_FB_PROT_HEADER_LEN from the MPAM_FB_MAX_MSG_SIZE definition. Thanks for having a thorough look! Cheers, Andre > >> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/ >> mpam_internal.h >> index a2193e7df57c..e926b7feb72a 100644 >> --- a/drivers/resctrl/mpam_internal.h >> +++ b/drivers/resctrl/mpam_internal.h >> @@ -77,7 +77,6 @@ struct mpam_msc { >>       /* Not modified after mpam_is_enabled() becomes true */ >>       enum mpam_msc_iface    iface; >>       struct mpam_pcc_chan    *pcc_chan; >> -    int            mpam_fb_msc_id;    /* in its own name space */ >>       u32            nrdy_usec; >>       cpumask_t        accessibility; >>       bool            has_extd_esr; >> @@ -532,6 +531,11 @@ int mpam_fb_send_write_request(struct mpam_msc >> *msc, u16 reg, u32 value); >>   int mpam_fb_get_protocol_version(struct mpam_msc *msc); >>   #define MPAM_FB_PROT_HEADER_LEN        sizeof(u32) >> +/* The longest message is MPAM_MSC_WRITE, with 4 parameters. */ >> +#define MPAM_FB_MAX_MSG_SIZE    (MPAM_FB_PROT_HEADER_LEN + 4 * >> sizeof(u32)) >> + >> +#define MPAM_FB_VERSION_MAJOR_MASK    GENMASK(31, 16) >> +#define MPAM_FB_VERSION_MINOR_MASK    GENMASK(15, 0) >>   /* >>    * MPAM MSCs have the following register layout. See: