From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A38C194C98; Thu, 19 Mar 2026 18:32:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773945141; cv=none; b=pJXdx/zB0Cs0adxkzfnSozTslUX0TrDbxEoGszbwGE31yozbFIiWeR1x6BbdaNYEGz+jl7g+vZxvhHamhGoVCh3ZLXrx5/VSUzU3MwYqcdMlRVrg2n6X7gC90VHMlrDvpVCnzFsf+nOl5qJEHAVMaxhepIFGTg2XfprdvJb9i/Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773945141; c=relaxed/simple; bh=q/AIFKBlYrlqgaIU+R+X2Kbm55lVUhw1nLQSCLmd6ew=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=EDWApP9FvLKDUyrbYkP0fXgMKLFP0p6bzhJnM1KtjsOx2K2vNn6/AqZh38yE5Hkl5ELMgyTy+3RdqSOEBUg/l96I44AMj5PW8tf7q4pAwsRv7r9Lp3hVOpu1Yy4YEeqO5rKx5cCvzxwB8uhNXAr9J0RJe/ztEmfhYVF8GuOS8Nw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SLfxJBQH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SLfxJBQH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2336C19424; Thu, 19 Mar 2026 18:32:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773945141; bh=q/AIFKBlYrlqgaIU+R+X2Kbm55lVUhw1nLQSCLmd6ew=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=SLfxJBQH3ZBwLVeaWFuXtr69z+ue66UBDBXapfmCGZU/5sePR0jM8ttItsExbkxXd fat6HASgQmW8lTt+q9Fv/u0XJTf3d3wZAiJLqrgzYHG5GWO4lK+JttBOqJXt5pwhQF w+6FlJPTdi3oKlG3m7NbTFgXf1aiA6jp7uCbZskZpkhz+sWDidVqJYVEsczF3/Cr0q 5HIA6+fCuzX4SwGeOuI+h7S9iLuLC57oeWrh6xVKPtDKceG2qv5E5rx2twVSmjZBNQ hX57e6N1IjMEwU/bgDkP0m8XkKB2jG/ioYVncpqZsFKATtztVHzIe50BPghhEOmL2B /aAbuSjpDjtvg== Date: Thu, 19 Mar 2026 13:32:19 -0500 From: Bjorn Helgaas To: Chengwen Feng Cc: Bjorn Helgaas , Catalin Marinas , Will Deacon , "Rafael J . Wysocki" , Jonathan Corbet , Shuah Khan , Huacai Chen , WANG Xuerui , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Juergen Gross , Boris Ostrovsky , Len Brown , Sunil V L , Mark Rutland , Jonathan Cameron , Kees Cook , Yanteng Si , Sean Christopherson , Kai Huang , Tom Lendacky , Thomas Huth , Thorsten Blum , Kevin Loughlin , Zheyun Shen , Peter Zijlstra , Pawan Gupta , Xin Li , "Ahmed S . Darwish" , Sohil Mehta , Ilkka Koskinen , Robin Murphy , James Clark , Besar Wicaksono , Ma Ke , Wei Huang , Andy Gospodarek , Somnath Kotur , punit.agrawal@oss.qualcomm.com, guohanjun@huawei.com, suzuki.poulose@arm.com, ryan.roberts@arm.com, chenl311@chinatelecom.cn, masahiroy@kernel.org, wangyuquan1236@phytium.com.cn, anshuman.khandual@arm.com, heinrich.schuchardt@canonical.com, Eric.VanTassell@amd.com, wangzhou1@hisilicon.com, wanghuiqiang@huawei.com, liuyonglong@huawei.com, linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, xen-devel@lists.xenproject.org, linux-acpi@vger.kernel.org, linux-perf-users@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v9 7/7] PCI/TPH: Fix get cpu steer-tag fail on ARM64 platform Message-ID: <20260319183219.GA519221@bhelgaas> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260319065735.45954-8-fengchengwen@huawei.com> Let's make the subject a little more specific, e.g., PCI/TPH: Pass ACPI Processor UID to Cache Locality _DSM On Thu, Mar 19, 2026 at 02:57:35PM +0800, Chengwen Feng wrote: > pcie_tph_get_cpu_st() is broken on ARM64: > 1. pcie_tph_get_cpu_st() passes cpu_uid to the PCI ACPI DSM method. > cpu_uid should be the ACPI Processor UID [1]. > 2. In BNXT, pcie_tph_get_cpu_st() is passed a cpu_uid obtained via > cpumask_first(irq->cpu_mask) - the logical CPU ID of a CPU core, > generated and managed by kernel (e.g., [0,255] for a system with 256 > logical CPU cores). > 3. On ARM64 platforms, ACPI assigns Processor UID to cores listed in the > MADT table, and this UID may not match the kernel's logical CPU ID. > When this occurs, the mismatch results in the wrong CPU steer-tag. > 4. On AMD x86 the logical CPU ID is identical to the ACPI Processor UID > so the mismatch is not seen. > > Resolution: > 1. Use acpi_get_cpu_uid() in pcie_tph_get_cpu_st() to translate from > logical CPU ID to ACPI Processor UID needed for the DSM call. > 2. Rename pcie_tpu_get_cpu_st() parameter from cpu_uid to cpu to > reflect that it is a logical CPU_ID. And simplify this, e.g., pcie_tph_get_cpu_st() uses the Query Cache Locality Features _DSM [1] to retrieve the TPH Steering Tag for memory associated with the CPU identified by its "cpu_uid" parameter, a Linux logical CPU ID. The _DSM requires a ACPI Processor UID, which pcie_tph_get_cpu_st() previously assumed was the same as the Linux logical CPU ID. This is true on x86 but not on arm64, so pcie_tph_get_cpu_st() failed on arm64. Convert the Linux logical CPU ID to the ACPI Processor UID with acpi_get_cpu_uid() before passing it to the _DSM. If there's a specific error message from BNXT or similar that is a symptom of this problem, it'd be nice to include that. Or if the problem was just poor performance because the _DSM returned the wrong Steering Tag, you could say something like: ... so pcie_tph_get_cpu_st() returned the wrong Steering Tag, resulting in poor network performance. > [1] According to ECN_TPH-ST_Revision_20200924 > (https://members.pcisig.com/wg/PCI-SIG/document/15470), the input > is defined as: "If the target is a processor, then this field > represents the ACPI Processor UID of the processor as specified in > the MADT. If the target is a processor container, then this field > represents the ACPI Processor UID of the processor container as > specified in the PPTT." > > Fixes: d2e8a34876ce ("PCI/TPH: Add Steering Tag support") > Cc: stable@vger.kernel.org > Signed-off-by: Chengwen Feng > Reviewed-by: Jonathan Cameron The patch looks good to me. Thanks for all your work on this! Reviewed-by: Bjorn Helgaas > --- > Documentation/PCI/tph.rst | 4 ++-- > drivers/pci/tph.c | 16 +++++++++++----- > include/linux/pci-tph.h | 4 ++-- > 3 files changed, 15 insertions(+), 9 deletions(-) > > diff --git a/Documentation/PCI/tph.rst b/Documentation/PCI/tph.rst > index e8993be64fd6..b6cf22b9bd90 100644 > --- a/Documentation/PCI/tph.rst > +++ b/Documentation/PCI/tph.rst > @@ -79,10 +79,10 @@ To retrieve a Steering Tag for a target memory associated with a specific > CPU, use the following function:: > > int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type type, > - unsigned int cpu_uid, u16 *tag); > + unsigned int cpu, u16 *tag); > > The `type` argument is used to specify the memory type, either volatile > -or persistent, of the target memory. The `cpu_uid` argument specifies the > +or persistent, of the target memory. The `cpu` argument specifies the > CPU where the memory is associated to. > > After the ST value is retrieved, the device driver can use the following > diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c > index ca4f97be7538..b67c9ad14bda 100644 > --- a/drivers/pci/tph.c > +++ b/drivers/pci/tph.c > @@ -236,21 +236,27 @@ static int write_tag_to_st_table(struct pci_dev *pdev, int index, u16 tag) > * with a specific CPU > * @pdev: PCI device > * @mem_type: target memory type (volatile or persistent RAM) > - * @cpu_uid: associated CPU id > + * @cpu: associated CPU id > * @tag: Steering Tag to be returned > * > * Return the Steering Tag for a target memory that is associated with a > - * specific CPU as indicated by cpu_uid. > + * specific CPU as indicated by cpu. > * > * Return: 0 if success, otherwise negative value (-errno) > */ > int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type mem_type, > - unsigned int cpu_uid, u16 *tag) > + unsigned int cpu, u16 *tag) > { > #ifdef CONFIG_ACPI > struct pci_dev *rp; > acpi_handle rp_acpi_handle; > union st_info info; > + u32 cpu_uid; > + int ret; > + > + ret = acpi_get_cpu_uid(cpu, &cpu_uid); > + if (ret != 0) > + return ret; > > rp = pcie_find_root_port(pdev); > if (!rp || !rp->bus || !rp->bus->bridge) > @@ -265,9 +271,9 @@ int pcie_tph_get_cpu_st(struct pci_dev *pdev, enum tph_mem_type mem_type, > > *tag = tph_extract_tag(mem_type, pdev->tph_req_type, &info); > > - pci_dbg(pdev, "get steering tag: mem_type=%s, cpu_uid=%d, tag=%#04x\n", > + pci_dbg(pdev, "get steering tag: mem_type=%s, cpu=%d, tag=%#04x\n", > (mem_type == TPH_MEM_TYPE_VM) ? "volatile" : "persistent", > - cpu_uid, *tag); > + cpu, *tag); > > return 0; > #else > diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h > index ba28140ce670..be68cd17f2f8 100644 > --- a/include/linux/pci-tph.h > +++ b/include/linux/pci-tph.h > @@ -25,7 +25,7 @@ int pcie_tph_set_st_entry(struct pci_dev *pdev, > unsigned int index, u16 tag); > int pcie_tph_get_cpu_st(struct pci_dev *dev, > enum tph_mem_type mem_type, > - unsigned int cpu_uid, u16 *tag); > + unsigned int cpu, u16 *tag); > void pcie_disable_tph(struct pci_dev *pdev); > int pcie_enable_tph(struct pci_dev *pdev, int mode); > u16 pcie_tph_get_st_table_size(struct pci_dev *pdev); > @@ -36,7 +36,7 @@ static inline int pcie_tph_set_st_entry(struct pci_dev *pdev, > { return -EINVAL; } > static inline int pcie_tph_get_cpu_st(struct pci_dev *dev, > enum tph_mem_type mem_type, > - unsigned int cpu_uid, u16 *tag) > + unsigned int cpu, u16 *tag) > { return -EINVAL; } > static inline void pcie_disable_tph(struct pci_dev *pdev) { } > static inline int pcie_enable_tph(struct pci_dev *pdev, int mode) > -- > 2.17.1 >