From: Matthias Brugger <mbrugger@suse.com>
To: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
Qian Cai <cai@lca.pw>,
catalin.marinas@arm.com
Cc: f.fainelli@gmail.com, wahrenst@gmx.net, marc.zyngier@arm.com,
will@kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Rob Herring <robh+dt@kernel.org>,
linux-rpi-kernel@lists.infradead.org, phill@raspberrypi.org,
Robin Murphy <Robin.Murphy@arm.com>,
Christoph Hellwig <hch@lst.de>,
linux-arm-kernel@lists.infradead.org, m.szyprowski@samsung.com
Subject: Re: [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE_DMA32
Date: Wed, 23 Oct 2019 09:11:59 +0200 [thread overview]
Message-ID: <796c6b37-67a0-9598-a146-5f298e0cd0c1@suse.com> (raw)
In-Reply-To: <1956a2c8f4911b2a7e2ba3c53506c0f06efb93f8.camel@suse.de>
On 22/10/2019 13:23, Nicolas Saenz Julienne wrote:
> On Mon, 2019-10-21 at 16:36 -0400, Qian Cai wrote:
>> I managed to get more information here,
>>
>> [ 0.000000] cma: dma_contiguous_reserve(limit c0000000)
>> [ 0.000000] cma: dma_contiguous_reserve: reserving 64 MiB for global area
>> [ 0.000000] cma: cma_declare_contiguous(size 0x0000000004000000, base
>> 0x0000000000000000, limit 0x00000000c0000000 alignment 0x0000000000000000)
>> [ 0.000000] cma: Failed to reserve 512 MiB
>>
>> Full dmesg:
>>
>> https://cailca.github.io/files/dmesg.txt
>
> OK I got it, reproduced it too.
>
> Here are the relevant logs:
>
> [ 0.000000] DMA [mem 0x00000000802f0000-0x00000000bfffffff]
> [ 0.000000] DMA32 [mem 0x00000000c0000000-0x00000000ffffffff]
> [ 0.000000] Normal [mem 0x0000000100000000-0x00000097fcffffff]
>
> As you can see ZONE_DMA spans from 0x00000000802f0000-0x00000000bfffffff which
> is slightly smaller than 1GB.
>
> [ 0.000000] crashkernel reserved: 0x000000009fe00000 - 0x00000000bfe00000 (512 MB)
>
> Here crashkernel reserved 512M in ZONE_DMA.
>
> [ 0.000000] cma: Failed to reserve 512 MiB
>
> CMA tried to allocate 512M in ZONE_DMA which fails as there is no enough space.
> Makes sense.
>
> A fix could be moving crashkernel reservations after CMA and then if unable to
> fit in ZONE_DMA try ZONE_DMA32 before bailing out. Maybe it's a little over the
> top, yet although most devices will be fine with ZONE_DMA32, the RPi4 needs
> crashkernel to be reserved in ZONE_DMA.
>
> My knowledge of Kdump is limited, so I'd love to see what Catalin has to say.
> Here's a tested patch of what I'm proposing:
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 120c26af916b..49f3c3a34ae2 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -76,6 +76,7 @@ phys_addr_t arm64_dma32_phys_limit __ro_after_init;
> static void __init reserve_crashkernel(void)
> {
> unsigned long long crash_base, crash_size;
> + phys_addr_t limit = arm64_dma_phys_limit;
> int ret;
>
> ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
> @@ -86,11 +87,14 @@ static void __init reserve_crashkernel(void)
>
> crash_size = PAGE_ALIGN(crash_size);
>
> +again:
> if (crash_base == 0) {
> /* Current arm64 boot protocol requires 2MB alignment */
> - crash_base = memblock_find_in_range(0, ARCH_LOW_ADDRESS_LIMIT,
> - crash_size, SZ_2M);
> - if (crash_base == 0) {
> + crash_base = memblock_find_in_range(0, limit, crash_size,
> SZ_2M);
> + if (!crash_base && limit == arm64_dma_phys_limit) {
> + limit = arm64_dma32_phys_limit;
> + goto again;
I'd try to avoid the goto.
Apart from that we should write some information message that the crashkernel
got reserved in arm64_dma_phys_limit. Otherwise RPi4 might break silently and
this will give the user at least a hint what happened.
Regards,
Matthias
> + } else if (!crash_base && limit == arm64_dma32_phys_limit) {
> pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> crash_size);
> return;
> @@ -448,13 +452,13 @@ void __init arm64_memblock_init(void)
> else
> arm64_dma32_phys_limit = PHYS_MASK + 1;
>
> - reserve_crashkernel();
> -
> reserve_elfcorehdr();
>
> high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>
> dma_contiguous_reserve(arm64_dma_phys_limit ? : arm64_dma32_phys_limit);
> +
> + reserve_crashkernel();
> }
>
> void __init bootmem_init(void)
>
>
> Regards,
> Nicolas
>
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next prev parent reply other threads:[~2019-10-23 7:12 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 18:25 [PATCH v6 0/4] Raspberry Pi 4 DMA addressing support Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 1/4] arm64: mm: use arm64_dma_phys_limit instead of calling max_zone_dma_phys() Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 2/4] arm64: rename variables used to calculate ZONE_DMA32's size Nicolas Saenz Julienne
2019-09-11 18:25 ` [PATCH v6 3/4] arm64: use both ZONE_DMA and ZONE_DMA32 Nicolas Saenz Julienne
2019-10-21 14:15 ` Qian Cai
2019-10-21 14:34 ` Nicolas Saenz Julienne
2019-10-21 14:46 ` Qian Cai
2019-10-21 17:01 ` Nicolas Saenz Julienne
2019-10-21 17:25 ` Qian Cai
2019-10-21 17:55 ` Nicolas Saenz Julienne
2019-10-21 20:36 ` Qian Cai
2019-10-22 11:23 ` Nicolas Saenz Julienne
2019-10-23 7:11 ` Matthias Brugger [this message]
2019-10-31 15:51 ` Catalin Marinas
2019-10-31 16:04 ` Nicolas Saenz Julienne
2019-10-31 18:02 ` Catalin Marinas
2019-10-31 18:11 ` Nicolas Saenz Julienne
2019-10-31 18:13 ` Catalin Marinas
2019-12-03 5:08 ` John Stultz
2019-12-03 5:38 ` John Stultz
2019-12-03 6:03 ` John Stultz
2019-12-03 10:12 ` Will Deacon
2019-12-03 11:19 ` Catalin Marinas
2019-09-11 18:25 ` [PATCH v6 4/4] mm: refresh ZONE_DMA and ZONE_DMA32 comments in 'enum zone_type' Nicolas Saenz Julienne
2019-10-01 16:05 ` [PATCH v6 0/4] Raspberry Pi 4 DMA addressing support Catalin Marinas
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