Re: [PATCH v13 6/8] arm64: kdump: reimplement crashkernel=X

From: Baoquan He <bhe@redhat.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: wangkefeng.wang@huawei.com, linux-doc@vger.kernel.org,
	chenzhou <chenzhou10@huawei.com>,
	catalin.marinas@arm.com, bhsharma@redhat.com,
	huawei.libin@huawei.com, guohanjun@huawei.com, will@kernel.org,
	corbet@lwn.net, mingo@redhat.com, dyoung@redhat.com,
	John.P.donnelly@oracle.com, arnd@arndb.de, xiexiuqi@huawei.com,
	horms@verge.net.au, tglx@linutronix.de,
	linux-arm-kernel@lists.infradead.org, kexec@lists.infradead.org,
	linux-kernel@vger.kernel.org, robh+dt@kernel.org,
	james.morse@arm.com, prabhakar.pkin@gmail.com,
	nsaenzjulienne@suse.de
Subject: Re: [PATCH v13 6/8] arm64: kdump: reimplement crashkernel=X
Date: Thu, 12 Nov 2020 16:36:45 +0800	[thread overview]
Message-ID: <20201112083645.GL8486@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20201112082509.GL4758@kernel.org>

On 11/12/20 at 10:25am, Mike Rapoport wrote:
> On Wed, Nov 11, 2020 at 09:54:48PM +0800, Baoquan He wrote:
> > On 11/11/20 at 09:27pm, chenzhou wrote:
> > > Hi Baoquan,
> > ...
> > > >>  #ifdef CONFIG_CRASH_DUMP
> > > >>  static int __init early_init_dt_scan_elfcorehdr(unsigned long node,
> > > >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> > > >> index 1c0f3e02f731..c55cee290bbb 100644
> > > >> --- a/arch/arm64/mm/mmu.c
> > > >> +++ b/arch/arm64/mm/mmu.c
> > > >> @@ -488,6 +488,10 @@ static void __init map_mem(pgd_t *pgdp)
> > > >>  	 */
> > > >>  	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);
> > > >>  #ifdef CONFIG_KEXEC_CORE
> > > >> +	if (crashk_low_res.end)
> > > >> +		memblock_mark_nomap(crashk_low_res.start,
> > > >> +				    resource_size(&crashk_low_res));
> > > >> +
> > > >>  	if (crashk_res.end)
> > > >>  		memblock_mark_nomap(crashk_res.start,
> > > >>  				    resource_size(&crashk_res));
> > > >> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> > > >> index d39892bdb9ae..cdef7d8c91a6 100644
> > > >> --- a/kernel/crash_core.c
> > > >> +++ b/kernel/crash_core.c
> > > >> @@ -321,7 +321,7 @@ int __init parse_crashkernel_low(char *cmdline,
> > > >>  
> > > >>  int __init reserve_crashkernel_low(void)
> > > >>  {
> > > >> -#ifdef CONFIG_X86_64
> > > >> +#if defined(CONFIG_X86_64) || defined(CONFIG_ARM64)
> > > > Not very sure if a CONFIG_64BIT checking is better.
> > > If doing like this, there may be some compiling errors for other 64-bit kernel, such as mips.
> > > >
> > > >>  	unsigned long long base, low_base = 0, low_size = 0;
> > > >>  	unsigned long low_mem_limit;
> > > >>  	int ret;
> > > >> @@ -362,12 +362,14 @@ int __init reserve_crashkernel_low(void)
> > > >>  
> > > >>  	crashk_low_res.start = low_base;
> > > >>  	crashk_low_res.end   = low_base + low_size - 1;
> > > >> +#ifdef CONFIG_X86_64
> > > >>  	insert_resource(&iomem_resource, &crashk_low_res);
> > > >> +#endif
> > > >>  #endif
> > > >>  	return 0;
> > > >>  }
> > > >>  
> > > >> -#ifdef CONFIG_X86
> > > >> +#if defined(CONFIG_X86) || defined(CONFIG_ARM64)
> > > > Should we make this weak default so that we can remove the ARCH config?
> > > The same as above, some arch may not support kdump, in that case,  compiling errors occur.
> > 
> > OK, not sure if other people have better idea, oterwise, we can leave with it. 
> > Thanks for telling.
> 
> I think it would be better to have CONFIG_ARCH_WANT_RESERVE_CRASH_KERNEL
> in arch/Kconfig and select this by X86 and ARM64.
> 
> Since reserve_crashkernel() implementations are quite similart on other
> architectures as well, we can have more users of this later.

Yes, this sounds like a nice way.

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