From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Fleming Subject: Re: [PATCH V4 1/4] efi: x86: rearrange efi_mem_attributes() Date: Mon, 15 Jun 2015 18:09:57 +0100 Message-ID: <20150615170957.GC17685@codeblueprint.co.uk> References: <1434157307-32318-1-git-send-email-zjzhang@codeaurora.org> <1434157307-32318-2-git-send-email-zjzhang@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1434157307-32318-2-git-send-email-zjzhang@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: "Jonathan (Zhixiong) Zhang" Cc: Matt Fleming , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, ying.huang@intel.com, fu.wei@linaro.org, al.stone@linaro.org, bp@alien8.de, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-efi@vger.kernel.org On Fri, 12 Jun, at 06:01:44PM, Jonathan (Zhixiong) Zhang wrote: > From: "Jonathan (Zhixiong) Zhang" > > x86 and ia64 implement efi_mem_attributes() differently. This > function needs to be available for other arch (such as arm64) > as well, such as for the purpose of ACPI/APEI. > > ia64 efi does not setup memmap variable and does not set > EFI_MEMMAP flag, so it needs to have its unique implementation > of efi_mem_attributes(). Something like the above paragraph... > @@ -517,3 +517,21 @@ char * __init efi_md_typeattr_format(char *buf, size_t size, > attr & EFI_MEMORY_UC ? "UC" : ""); > return buf; > } needs to go here, i.e. as documentation for efi_mem_atributes(). You need to explain why this function is marked as __weak at the function definition site. > +u64 __weak efi_mem_attributes(unsigned long phys_addr) > +{ > + efi_memory_desc_t *md; > + void *p; > + > + if (!efi_enabled(EFI_MEMMAP)) > + return 0; > + > + for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) { > + md = p; > + if ((md->phys_addr <= phys_addr) && > + (phys_addr < (md->phys_addr + > + (md->num_pages << EFI_PAGE_SHIFT)))) > + return md->attribute; > + } > + return 0; > +} because otherwise people are going to read this in the future and think, "efi_mem_attribute() doesn't quite work how I want it to for my arch, but it's __weak, so I'll override it" which is absolutely not the practice we should be promoting. How about something like this, /* * efi_mem_attributes - lookup memmap attributes for physical address * @phys_addr: the physical address to lookup * * Search in the EFI memory map for the region covering * @phys_addr. Returns the EFI memory attributes if the region * was found in the memory map, 0 otherwise. * * Despite being marked __weak most architectures should *not* * override this function. It is __weak solely for the benefit * of ia64 which has a funky EFI memory map that doesn't work * the same way as other architectures. */ -- Matt Fleming, Intel Open Source Technology Center