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Date:   Thu, 17 Mar 2022 11:47:31 +0800
From:   Baoquan He <bhe@redhat.com>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@huawei.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,
        Catalin Marinas <catalin.marinas@arm.com>,
        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 v21 3/5] arm64: kdump: reimplement crashkernel=X
Message-ID: <YjKvUz+dKRkyxUAd@MiWiFi-R3L-srv>
References: <20220227030717.1464-1-thunder.leizhen@huawei.com>
 <20220227030717.1464-4-thunder.leizhen@huawei.com>
 <YjHUAi0xrUy+qk/L@MiWiFi-R3L-srv>
 <7d7a3e70-6a46-b722-ef48-7206a47185dd@huawei.com>
 <YjKeuFGtjI7944uy@MiWiFi-R3L-srv>
 <05a96786-cfe8-029f-f29a-60fb94129f91@huawei.com>
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On 03/17/22 at 11:19am, Leizhen (ThunderTown) wrote:
> 
> 
> On 2022/3/17 10:36, Baoquan He wrote:
> > On 03/16/22 at 09:11pm, Leizhen (ThunderTown) wrote:
> >>
> >>
> >> On 2022/3/16 20:11, Baoquan He wrote:
> >>> On 02/27/22 at 11:07am, Zhen Lei wrote:
> > ...... 
> > 
> >>> Hi leizhen,
> >>>
> >>> I made change on reserve_crashkenrel(), inline comment may be slow.
> >>> Please check and consider if they can be taken.
> >>
> >> That's great. Thank you very much.
> >>
> >>>
> >>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> >>> index 30ae6638ff54..f96351da1e3e 100644
> >>> --- a/arch/arm64/mm/init.c
> >>> +++ b/arch/arm64/mm/init.c
> >>> @@ -109,38 +109,43 @@ static int __init reserve_crashkernel_low(unsigned long long low_size)
> >>>   * This function reserves memory area given in "crashkernel=" kernel command
> >>>   * line parameter. The memory reserved is used by dump capture kernel when
> >>>   * primary kernel is crashing.
> >>> + *
> >>> + * NOTE: Reservation of crashkernel,low is special since its existence
> >>> + * is not independent, need rely on the existence of crashkernel,high.
> >>> + * Hence there are different cases for crashkernel,low reservation:
> > 
> > Considering to update the 3rd line as below:
> > 
> >  * NOTE: Reservation of crashkernel,low is special since its existence
> >  * is not independent, need rely on the existence of crashkernel,high.
> >  * Here, four cases of crashkernel,low reservation are summarized: 
> 
> OK. How about change "crashkernel,low" to "crashkernel low memory"?
> "crashkernel=Y,low", "crashkernel=,low" and "crashkernel,low" are very similar,
> may dazzle the reader.

Fine by me. 'crashkernel low memory' is formal, just make sentence a
little longer. Please take what you think fitter.

> 
> > 
> >>> + * 1) crashkernel=Y,low is specified explicitly, crashkernel,low takes Y;
> >>> + * 2) crashkernel=,low is not given, while crashkernel=,high is specified,
> >>> + *    take the default crashkernel,low value;
> >>> + * 3) crashkernel=X is specified, while fallback to get a memory region
> >>> + *    in high memory, take the default crashkernel,low value;
> >>> + * 4) crashkernel='invalid value',low is specified, failed the whole
> >>> + *    crashkernel reservation and bail out.
> >>>   */
> >>>  static void __init reserve_crashkernel(void)
> >>>  {
> >>>  	unsigned long long crash_base, crash_size;
> >>>  	unsigned long long crash_low_size;
> >>>  	unsigned long long crash_max = CRASH_ADDR_LOW_MAX;
> >>> -	int ret;
> >>>  	bool fixed_base, high = false;
> >>>  	char *cmdline = boot_command_line;
> >>> +	int ret;
> >>>  
> >>>  	/* crashkernel=X[@offset] */
> >>>  	ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
> >>>  				&crash_size, &crash_base);
> >>>  	if (ret || !crash_size) {
> >>> -		/* crashkernel=X,high */
> >>>  		ret = parse_crashkernel_high(cmdline, 0, &crash_size, &crash_base);
> >>>  		if (ret || !crash_size)
> >>>  			return;
> >>>  
> >>> -		/* crashkernel=Y,low */
> >>>  		ret = parse_crashkernel_low(cmdline, 0, &crash_low_size, &crash_base);
> >>>  		if (ret == -ENOENT)
> >>> -			/*
> >>> -			 * crashkernel=Y,low is not specified explicitly, use
> >>> -			 * default size automatically.
> >>> -			 */
> >>> +			/* case #2 of crashkernel,low reservation */
> >>>  			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> >>>  		else if (ret)
> >>> -			/* crashkernel=Y,low is specified but Y is invalid */
> >>> +			/* case #4 of crashkernel,low reservation */
> >>>  			return;
> >>>  
> >>> -		/* Mark crashkernel=X,high is specified */
> >>>  		high = true;
> >>>  		crash_max = CRASH_ADDR_HIGH_MAX;
> >>>  	}
> >>> @@ -148,7 +153,6 @@ static void __init reserve_crashkernel(void)
> >>>  	fixed_base = !!crash_base;
> >>>  	crash_size = PAGE_ALIGN(crash_size);
> >>>  
> >>> -	/* User specifies base address explicitly. */
> >>>  	if (fixed_base)
> >>>  		crash_max = crash_base + crash_size;
> >>>  
> >>> @@ -172,11 +176,7 @@ static void __init reserve_crashkernel(void)
> >>>  	}
> >>>  
> >>>  	if (crash_base >= SZ_4G) {
> >>> -		/*
> >>> -		 * For case crashkernel=X, low memory is not enough and fall
> >>> -		 * back to reserve specified size of memory above 4G, try to
> >>> -		 * allocate minimum required memory below 4G again.
> >>> -		 */
> >>> +		/* case #3 of crashkernel,low reservation */
> >>>  		if (!high)
> >>>  			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> >>>  
> >>>
> >>>>  
> >>>> -	/* Current arm64 boot protocol requires 2MB alignment */
> >>>> -	crash_base = memblock_phys_alloc_range(crash_size, SZ_2M,
> >>>> +retry:
> >>>> +	crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
> >>>>  					       crash_base, crash_max);
> >>>>  	if (!crash_base) {
> >>>> +		/*
> >>>> +		 * Attempt to fully allocate low memory failed, fall back
> >>>> +		 * to high memory, the minimum required low memory will be
> >>>> +		 * reserved later.
> >>>> +		 */
> >>>> +		if (!fixed_base && (crash_max == CRASH_ADDR_LOW_MAX)) {
> >>>> +			crash_max = CRASH_ADDR_HIGH_MAX;
> >>>> +			goto retry;
> >>>> +		}
> >>>> +
> >>>>  		pr_warn("cannot allocate crashkernel (size:0x%llx)\n",
> >>>>  			crash_size);
> >>>>  		return;
> >>>>  	}
> >>>>  
> >>>> +	if (crash_base >= SZ_4G) {
> >>>> +		/*
> >>>> +		 * For case crashkernel=X, low memory is not enough and fall
> >>>> +		 * back to reserve specified size of memory above 4G, try to
> >>>> +		 * allocate minimum required memory below 4G again.
> >>>> +		 */
> >>>> +		if (!high)
> >>>> +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> >>>> +
> >>>> +		if (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);
> >>>>  
> >>>> @@ -107,6 +194,9 @@ 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
> >>>>
> >>>
> >>> .
> >>>
> >>
> >> -- 
> >> Regards,
> >>   Zhen Lei
> >>
> > 
> > .
> > 
> 
> -- 
> Regards,
>   Zhen Lei
>