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Wed, 14 Apr 2021 20:06:44 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id C300961154; Wed, 14 Apr 2021 20:06:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618430801; bh=MUyogixBd6zIDiaR0VtNwpReVA3q8yetd1FUh51s0mY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LVDXufk2mGL1uurwUlE0uKYfGUCD/t4dulxRWu+0ZVD/Y0y1eVtNu69zMAHUO41OP mh760Of0rNXS9bxqsSMLBPa1WLFeVJyldHM7wX6MhoavPNsSNpM2jZqEYCYO8dfVsg b3GmAX4DMY/u9HG19F7urXJLTPs3GXiMuO5TWcv6/GEQwqdIE8He+jYu60ulNZihyT 8jFHXJ1sUyZyKm9a9ITlIDmRgu+aBB1yDlgnjws89Omum+Eosc+Pv5A9npX92lBWal caFG9N9gAfrmPqdD6arq0PCOtSFtWWu/34fGD/Np9/8IltuT2PW6Abq/ok928hEM77 9A8v8fK9P6xkw== Date: Wed, 14 Apr 2021 23:06:33 +0300 From: Mike Rapoport To: David Hildenbrand Cc: linux-arm-kernel@lists.infradead.org, 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 Subject: Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved pages Message-ID: References: <20210407172607.8812-1-rppt@kernel.org> <20210407172607.8812-2-rppt@kernel.org> <0c48f98c-7454-1458-15a5-cc5a7e1fb7cd@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0c48f98c-7454-1458-15a5-cc5a7e1fb7cd@redhat.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210414_130642_759699_01D1E926 X-CRM114-Status: GOOD ( 38.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Apr 14, 2021 at 05:12:11PM +0200, David Hildenbrand wrote: > 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. The pages should not be accessed as normal memory so they do not have a direct (or in ARMish linear) mapping and are never given to buddy. After looking at ACPI standard I don't see a fundamental reason for this but they've already made this mess and we need to cope with it. > I can spot that we want to export such memory like any special memory > thingy/hole in /proc/iomem -- "reserved", which makes sense. It does, but let's wait with /proc/iomem changes. We don't really have a 100% consistent view of it on different architectures, so adding yet another type there does not seem, well, urgent. > 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. I agree that there is a lot of commonality between NOMAP and reserved. The problem is that even semantics for reserved is different between architectures. Moreover, on the same architecture there could be E820_TYPE_RESERVED and memblock.reserved with different properties. I'd really prefer moving in baby steps here because any change in the boot mm can bear several month of early hangs debugging ;-) > > 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 -- Sincerely yours, Mike. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel