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[50.195.43.97]) by smtp.gmail.com with ESMTPSA id b22sm11718512qkk.45.2021.03.22.11.41.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Mar 2021 11:41:32 -0700 (PDT) Subject: Re: [PATCH v3 2/2] arm64: mm: reserve CMA and crashkernel in ZONE_DMA32 From: Jon Masters To: Nicolas Saenz Julienne , catalin.marinas@arm.com, linux-kernel@vger.kernel.org Cc: Qian Cai , Will Deacon , linux-arm-kernel@lists.infradead.org References: <20191107095611.18429-1-nsaenzjulienne@suse.de> <20191107095611.18429-3-nsaenzjulienne@suse.de> <4f094513-507d-566d-a0e2-a30ea36f64c9@jonmasters.org> Organization: World Organi{s,z}ation of Broken Dreams Message-ID: Date: Mon, 22 Mar 2021 14:40:48 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <4f094513-507d-566d-a0e2-a30ea36f64c9@jonmasters.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 3/22/21 2:34 PM, Jon Masters wrote: > Hi Nicolas, > > On 11/7/19 4:56 AM, Nicolas Saenz Julienne wrote: >> With the introduction of ZONE_DMA in arm64 we moved the default CMA and >> crashkernel reservation into that area. This caused a regression on big >> machines that need big CMA and crashkernel reservations. Note that >> ZONE_DMA is only 1GB big. >> >> Restore the previous behavior as the wide majority of devices are OK >> with reserving these in ZONE_DMA32. The ones that need them in ZONE_DMA >> will configure it explicitly. >> >> Reported-by: Qian Cai >> Signed-off-by: Nicolas Saenz Julienne >> --- >>   arch/arm64/mm/init.c | 4 ++-- >>   1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c >> index 580d1052ac34..8385d3c0733f 100644 >> --- a/arch/arm64/mm/init.c >> +++ b/arch/arm64/mm/init.c >> @@ -88,7 +88,7 @@ static void __init reserve_crashkernel(void) >>       if (crash_base == 0) { >>           /* Current arm64 boot protocol requires 2MB alignment */ >> -        crash_base = memblock_find_in_range(0, ARCH_LOW_ADDRESS_LIMIT, >> +        crash_base = memblock_find_in_range(0, arm64_dma32_phys_limit, >>                   crash_size, SZ_2M); >>           if (crash_base == 0) { >>               pr_warn("cannot allocate crashkernel (size:0x%llx)\n", >> @@ -454,7 +454,7 @@ void __init arm64_memblock_init(void) >>       high_memory = __va(memblock_end_of_DRAM() - 1) + 1; >> -    dma_contiguous_reserve(arm64_dma_phys_limit ? : >> arm64_dma32_phys_limit); >> +    dma_contiguous_reserve(arm64_dma32_phys_limit); >>   } >>   void __init bootmem_init(void) > > Can we get a bit more of a backstory about what the regression was on > larger machines? If the 32-bit DMA region is too small, but the machine > otherwise has plenty of memory, the crashkernel reservation will fail. > Most e.g. enterprise users aren't going to respond to that situation by > determining the placement manually, they'll just not have a crashkernel. Nevermind, looks like Catalin already changed this logic in Jan 2021 by removing arm64_dma32_phys_limit and I'm out of date. Jon. -- Computer Architect