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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hDPpF-0002N0-2V; Mon, 08 Apr 2019 08:40:21 +0000 Received: from szxga06-in.huawei.com ([45.249.212.32] helo=huawei.com) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hDPpA-0002Ha-Fo; Mon, 08 Apr 2019 08:40:18 +0000 Received: from DGGEMS401-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id D3C144B3660DE31C2D9C; Mon, 8 Apr 2019 16:40:10 +0800 (CST) Received: from [127.0.0.1] (10.177.131.64) by DGGEMS401-HUB.china.huawei.com (10.3.19.201) with Microsoft SMTP Server id 14.3.408.0; Mon, 8 Apr 2019 16:40:02 +0800 Subject: Re: [PATCH 2/3] arm64: kdump: support more than one crash kernel regions To: Mike Rapoport References: <20190403030546.23718-1-chenzhou10@huawei.com> <20190403030546.23718-3-chenzhou10@huawei.com> <20190403112929.GA7715@rapoport-lnx> <20190404144408.GA6433@rapoport-lnx> <783b8712-ddb1-a52b-81ee-0c6a216e5b7d@huawei.com> <4b188535-c12d-e05b-9154-2c2d580f903b@huawei.com> <20190408065711.GA8403@rapoport-lnx> From: Chen Zhou Message-ID: <3fc772a2-292b-9c2a-465f-eabe86961dfd@huawei.com> Date: Mon, 8 Apr 2019 16:39:59 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20190408065711.GA8403@rapoport-lnx> X-Originating-IP: [10.177.131.64] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190408_014016_706236_6EE1DE10 X-CRM114-Status: GOOD ( 19.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: wangkefeng.wang@huawei.com, ard.biesheuvel@linaro.org, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, takahiro.akashi@linaro.org, akpm@linux-foundation.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Mike, On 2019/4/8 14:57, Mike Rapoport wrote: > Hi, > > On Fri, Apr 05, 2019 at 11:47:27AM +0800, Chen Zhou wrote: >> Hi Mike, >> >> On 2019/4/5 10:17, Chen Zhou wrote: >>> Hi Mike, >>> >>> On 2019/4/4 22:44, Mike Rapoport wrote: >>>> Hi, >>>> >>>> On Wed, Apr 03, 2019 at 09:51:27PM +0800, Chen Zhou wrote: >>>>> Hi Mike, >>>>> >>>>> On 2019/4/3 19:29, Mike Rapoport wrote: >>>>>> On Wed, Apr 03, 2019 at 11:05:45AM +0800, Chen Zhou wrote: >>>>>>> After commit (arm64: kdump: support reserving crashkernel above 4G), >>>>>>> there may be two crash kernel regions, one is below 4G, the other is >>>>>>> above 4G. >>>>>>> >>>>>>> Crash dump kernel reads more than one crash kernel regions via a dtb >>>>>>> property under node /chosen, >>>>>>> linux,usable-memory-range = >>>>>>> >>>>>>> Signed-off-by: Chen Zhou >>>>>>> --- >>>>>>> arch/arm64/mm/init.c | 37 +++++++++++++++++++++++++------------ >>>>>>> include/linux/memblock.h | 1 + >>>>>>> mm/memblock.c | 40 ++++++++++++++++++++++++++++++++++++++++ >>>>>>> 3 files changed, 66 insertions(+), 12 deletions(-) >>>>>>> >>>>>>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c >>>>>>> index ceb2a25..769c77a 100644 >>>>>>> --- a/arch/arm64/mm/init.c >>>>>>> +++ b/arch/arm64/mm/init.c >>>>>>> @@ -64,6 +64,8 @@ EXPORT_SYMBOL(memstart_addr); >>>>>>> phys_addr_t arm64_dma_phys_limit __ro_after_init; >>>>>>> >>>>>>> #ifdef CONFIG_KEXEC_CORE >>>>>>> +# define CRASH_MAX_USABLE_RANGES 2 >>>>>>> + >>>>>>> static int __init reserve_crashkernel_low(void) >>>>>>> { >>>>>>> unsigned long long base, low_base = 0, low_size = 0; >>>>>>> @@ -346,8 +348,8 @@ static int __init early_init_dt_scan_usablemem(unsigned long node, >>>>>>> const char *uname, int depth, void *data) >>>>>>> { >>>>>>> struct memblock_region *usablemem = data; >>>>>>> - const __be32 *reg; >>>>>>> - int len; >>>>>>> + const __be32 *reg, *endp; >>>>>>> + int len, nr = 0; >>>>>>> >>>>>>> if (depth != 1 || strcmp(uname, "chosen") != 0) >>>>>>> return 0; >>>>>>> @@ -356,22 +358,33 @@ static int __init early_init_dt_scan_usablemem(unsigned long node, >>>>>>> if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells))) >>>>>>> return 1; >>>>>>> >>>>>>> - usablemem->base = dt_mem_next_cell(dt_root_addr_cells, ®); >>>>>>> - usablemem->size = dt_mem_next_cell(dt_root_size_cells, ®); >>>>>>> + endp = reg + (len / sizeof(__be32)); >>>>>>> + while ((endp - reg) >= (dt_root_addr_cells + dt_root_size_cells)) { >>>>>>> + usablemem[nr].base = dt_mem_next_cell(dt_root_addr_cells, ®); >>>>>>> + usablemem[nr].size = dt_mem_next_cell(dt_root_size_cells, ®); >>>>>>> + >>>>>>> + if (++nr >= CRASH_MAX_USABLE_RANGES) >>>>>>> + break; >>>>>>> + } >>>>>>> >>>>>>> return 1; >>>>>>> } >>>>>>> >>>>>>> static void __init fdt_enforce_memory_region(void) >>>>>>> { >>>>>>> - struct memblock_region reg = { >>>>>>> - .size = 0, >>>>>>> - }; >>>>>>> - >>>>>>> - of_scan_flat_dt(early_init_dt_scan_usablemem, ®); >>>>>>> - >>>>>>> - if (reg.size) >>>>>>> - memblock_cap_memory_range(reg.base, reg.size); >>>>>>> + int i, cnt = 0; >>>>>>> + struct memblock_region regs[CRASH_MAX_USABLE_RANGES]; >>>>>>> + >>>>>>> + memset(regs, 0, sizeof(regs)); >>>>>>> + of_scan_flat_dt(early_init_dt_scan_usablemem, regs); >>>>>>> + >>>>>>> + for (i = 0; i < CRASH_MAX_USABLE_RANGES; i++) >>>>>>> + if (regs[i].size) >>>>>>> + cnt++; >>>>>>> + else >>>>>>> + break; >>>>>>> + if (cnt) >>>>>>> + memblock_cap_memory_ranges(regs, cnt); >>>>>> >>>>>> Why not simply call memblock_cap_memory_range() for each region? >>>>> >>>>> Function memblock_cap_memory_range() removes all memory type ranges except specified range. >>>>> So if we call memblock_cap_memory_range() for each region simply, there will be no usable-memory >>>>> on kdump capture kernel. >>>> >>>> Thanks for the clarification. >>>> I still think that memblock_cap_memory_ranges() is overly complex. >>>> >>>> How about doing something like this: >>>> >>>> Cap the memory range for [min(regs[*].start, max(regs[*].end)] and then >>>> removing the range in the middle? >>> >>> Yes, that would be ok. But that would do one more memblock_cap_memory_range operation. >>> That is, if there are n regions, we need to do (n + 1) operations, which doesn't seem to >>> matter. >>> >>> I agree with you, your idea is better. >>> >>> Thanks, >>> Chen Zhou >> >> Sorry, just ignore my previous reply, I got that wrong. >> >> I think it carefully, we can cap the memory range for [min(regs[*].start, max(regs[*].end)] >> firstly. But how to remove the middle ranges, we still can't use memblock_cap_memory_range() >> directly and the extra remove operation may be complex. >> >> For more than one regions, i think add a new memblock_cap_memory_ranges() may be better. >> Besides, memblock_cap_memory_ranges() is also applicable for one region. >> >> How about replace memblock_cap_memory_range() with memblock_cap_memory_ranges()? > > arm64 is the only user of both MEMBLOCK_NOMAP and memblock_cap_memory_range() > and I don't expect other architectures will use these interfaces. > It seems that capping the memory for arm64 crash kernel the way I've > suggested can be implemented in fdt_enforce_memory_region(). If we'd ever > need such functionality elsewhere or CRASH_MAX_USABLE_RANGES will need to > grow we'll rethink the solution. Ok, i will implement that in fdt_enforce_memory_region() in next version. And we will support at most two crash kernel regions now. Thanks, Chen Zhou > >> Thanks, >> Chen Zhou > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel