Re: [PATCH v24 3/6] arm64: kdump: Reimplement crashkernel=X

From: Baoquan He <bhe@redhat.com>
To: Zhen Lei <thunder.leizhen@huawei.com>,
	Catalin Marinas <catalin.marinas@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org, Dave Young <dyoung@redhat.com>,
	Vivek Goyal <vgoyal@redhat.com>,
	Eric Biederman <ebiederm@xmission.com>,
	kexec@lists.infradead.org, Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	devicetree@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
	linux-doc@vger.kernel.org, Randy Dunlap <rdunlap@infradead.org>,
	Feng Zhou <zhoufeng.zf@bytedance.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	Chen Zhou <dingguo.cz@antgroup.com>,
	John Donnelly <John.p.donnelly@oracle.com>,
	Dave Kleikamp <dave.kleikamp@oracle.com>
Subject: Re: [PATCH v24 3/6] arm64: kdump: Reimplement crashkernel=X
Date: Sat, 7 May 2022 07:10:32 +0800	[thread overview]
Message-ID: <20220506231032.GA122876@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20220506114402.365-4-thunder.leizhen@huawei.com>

On 05/06/22 at 07:43pm, Zhen Lei wrote:
......  
> @@ -118,8 +162,7 @@ static void __init reserve_crashkernel(void)
>  	if (crash_base)
>  		crash_max = crash_base + crash_size;
>  
> -	/* Current arm64 boot protocol requires 2MB alignment */
> -	crash_base = memblock_phys_alloc_range(crash_size, SZ_2M,
> +	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
>  					       crash_base, crash_max);
>  	if (!crash_base) {
>  		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> @@ -127,6 +170,11 @@ static void __init reserve_crashkernel(void)
>  		return;
>  	}
>  

There's corner case missed, e.g
1) ,high and ,low are specified, CONFIG_ZONE_DMA|DMA32 is not enabled;
2) ,high and ,low are specified, the whole system memory is under 4G.

Below judgement can filter them away:

	if (crash_base > arm64_dma_phys_limit && crash_low_size &&
	    reserve_crashkernel_low(crash_low_size)) {

What's your opinion? Leave it and add document to notice user, or fix it
with code change?

I would suggest merging this series, Lei can add this corner case
handling on top. Since this is a newly added support, we don't have
to make it one step. Doing step by step can make reviewing easier.

> +	if (crash_low_size && reserve_crashkernel_low(crash_low_size)) {
> +		memblock_phys_free(crash_base, crash_size);
> +		return;
> +	}
> +
>  	pr_info("crashkernel reserved: 0x%016llx - 0x%016llx (%lld MB)\n",
>  		crash_base, crash_base + crash_size, crash_size >> 20);
>  
> @@ -135,6 +183,9 @@ static void __init reserve_crashkernel(void)
>  	 * map. Inform kmemleak so that it won't try to access it.
>  	 */
>  	kmemleak_ignore_phys(crash_base);
> +	if (crashk_low_res.end)
> +		kmemleak_ignore_phys(crashk_low_res.start);
> +
>  	crashk_res.start = crash_base;
>  	crashk_res.end = crash_base + crash_size - 1;
>  	insert_resource(&iomem_resource, &crashk_res);
> -- 
> 2.25.1
> 