From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hanjun Guo Subject: Re: [PATCH v3 05/12] arm64, acpi, numa: NUMA support based on SRAT and SLIT Date: Thu, 28 Jan 2016 11:16:34 +0800 Message-ID: <56A98812.4060506@huawei.com> References: <1453541967-3744-1-git-send-email-guohanjun@huawei.com> <1453541967-3744-6-git-send-email-guohanjun@huawei.com> <20160125102148.GE24726@rric.localdomain> <56A86DCF.1020205@huawei.com> <20160127140109.GQ24726@rric.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: Received: from szxga03-in.huawei.com ([119.145.14.66]:32010 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933401AbcA1DQz (ORCPT ); Wed, 27 Jan 2016 22:16:55 -0500 In-Reply-To: <20160127140109.GQ24726@rric.localdomain> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Robert Richter Cc: "Rafael J. Wysocki" , Will Deacon , Catalin Marinas , linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Ganapatrao Kulkarni , Lorenzo Pieralisi , Shannon Zhao , Steve Capper , Mark Rutland , Hanjun Guo On 2016/1/27 22:01, Robert Richter wrote: > On 27.01.16 15:12:15, Hanjun Guo wrote: >> On 2016/1/25 18:21, Robert Richter wrote: >>> On 23.01.16 17:39:20, Hanjun Guo wrote: >>>> diff --git a/arch/arm64/kernel/acpi_numa.c b/arch/arm64/kernel/acpi_numa.c >>>> new file mode 100644 >>>> index 0000000..f7f7533 >>>> --- /dev/null >>>> +++ b/arch/arm64/kernel/acpi_numa.c >>>> +/* Callback for parsing of the Proximity Domain <-> Memory Area mappings */ >>>> +int __init acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma) >>>> +{ >>>> + u64 start, end; >>>> + int node, pxm; >>>> + >>>> + if (srat_disabled()) >>>> + return -EINVAL; >>>> + >>>> + if (ma->header.length != sizeof(struct acpi_srat_mem_affinity)) { >>> Must be: >>> >>> ma->header.length < sizeof(struct acpi_srat_mem_affinity)) { >>> >>> Allow extensions to struct acpi_srat_mem_affinity in newer versions. >> Hmm, I think we need to remove the check here now. > No, we might have an out-of-bound access then. > >> There are three cases: >> >> - firmware ACPI version is consistent with the ACPICA one, then >> ma->header.length == sizeof(struct acpi_srat_mem_affinity ) >> >> - firmware ACPI version is not consistent with the ACPICA one, >> for example, struct acpi_srat_mem_affinity is extended in >> new ACI version, but the formware is using the older one, >> then it's ok to use >> ma->header.length < sizeof(struct acpi_srat_mem_affinity ) > The check above is ok as we need at least struct > acpi_srat_mem_affinity as it is now. > > If we later change the kernel to support multiple versions of struct > acpi_srat_mem_affinity, i.e. use data from an extended section, we > will need to add code to handle that. This will include support of > data with length < acpi_srat_mem_affinity, in this case we may not use > extended data. I checked the ACPI spec about memory affinity structure, it still have 10 bytes reserved for future use, so I think it's safe as you suggested for next few years. > >> - but if we use the older kernel + updated new firmware, >> then >> ma->header.length > sizeof(struct acpi_srat_mem_affinity ) >> will be the case, right? > Right, and this is a valid case not resulting in an error with my > suggestion above. Yes, I just mixed up those two cases. I will sync with Ganapat to prepare a new version and test it on x86 and IA64 to make sure this patch set don't break anything. Thanks Hanjun