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[91.12.100.112]) by smtp.gmail.com with ESMTPSA id z14sm334347wrt.54.2021.04.14.08.12.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Apr 2021 08:12:12 -0700 (PDT) To: Mike Rapoport , linux-arm-kernel@lists.infradead.org Cc: Anshuman Khandual , Ard Biesheuvel , Catalin Marinas , Marc Zyngier , Mark Rutland , Mike Rapoport , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20210407172607.8812-1-rppt@kernel.org> <20210407172607.8812-2-rppt@kernel.org> From: David Hildenbrand Organization: Red Hat Subject: Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved pages Message-ID: <0c48f98c-7454-1458-15a5-cc5a7e1fb7cd@redhat.com> Date: Wed, 14 Apr 2021 17:12:11 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210407172607.8812-2-rppt@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07.04.21 19:26, Mike Rapoport wrote: > From: Mike Rapoport > > The struct pages representing a reserved memory region are initialized > using reserve_bootmem_range() function. This function is called for each > reserved region just before the memory is freed from memblock to the buddy > page allocator. > > The struct pages for MEMBLOCK_NOMAP regions are kept with the default > values set by the memory map initialization which makes it necessary to > have a special treatment for such pages in pfn_valid() and > pfn_valid_within(). I assume these pages are never given to the buddy, because we don't have a direct mapping. So to the kernel, it's essentially just like a memory hole with benefits. I can spot that we want to export such memory like any special memory thingy/hole in /proc/iomem -- "reserved", which makes sense. I would assume that MEMBLOCK_NOMAP is a special type of *reserved* memory. IOW, that for_each_reserved_mem_range() should already succeed on these as well -- we should mark anything that is MEMBLOCK_NOMAP implicitly as reserved. Or are there valid reasons not to do so? What can anyone do with that memory? I assume they are pretty much useless for the kernel, right? Like other reserved memory ranges. > > Split out initialization of the reserved pages to a function with a > meaningful name and treat the MEMBLOCK_NOMAP regions the same way as the > reserved regions and mark struct pages for the NOMAP regions as > PageReserved. > > Signed-off-by: Mike Rapoport > --- > mm/memblock.c | 23 +++++++++++++++++++++-- > 1 file changed, 21 insertions(+), 2 deletions(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index afaefa8fc6ab..6b7ea9d86310 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -2002,6 +2002,26 @@ static unsigned long __init __free_memory_core(phys_addr_t start, > return end_pfn - start_pfn; > } > > +static void __init memmap_init_reserved_pages(void) > +{ > + struct memblock_region *region; > + phys_addr_t start, end; > + u64 i; > + > + /* initialize struct pages for the reserved regions */ > + for_each_reserved_mem_range(i, &start, &end) > + reserve_bootmem_region(start, end); > + > + /* and also treat struct pages for the NOMAP regions as PageReserved */ > + for_each_mem_region(region) { > + if (memblock_is_nomap(region)) { > + start = region->base; > + end = start + region->size; > + reserve_bootmem_region(start, end); > + } > + } > +} > + > static unsigned long __init free_low_memory_core_early(void) > { > unsigned long count = 0; > @@ -2010,8 +2030,7 @@ static unsigned long __init free_low_memory_core_early(void) > > memblock_clear_hotplug(0, -1); > > - for_each_reserved_mem_range(i, &start, &end) > - reserve_bootmem_region(start, end); > + memmap_init_reserved_pages(); > > /* > * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id > -- Thanks, David / dhildenb