Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 31 Mar 2023 07:32:54 +0800
From:   Baoquan He <bhe@redhat.com>
To:     "chenjiahao (C)" <chenjiahao16@huawei.com>
Cc:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        conor.dooley@microchip.com, guoren@kernel.org, heiko@sntech.de,
        bjorn@rivosinc.com, alex@ghiti.fr, akpm@linux-foundation.org,
        atishp@rivosinc.com, thunder.leizhen@huawei.com, horms@kernel.org,
        linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
        kexec@lists.infradead.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH -next v2 1/2] riscv: kdump: Implement
 crashkernel=X,[high,low]
Message-ID: <ZCYcJos4MLBvpP9/@MiWiFi-R3L-srv>
References: <20230328115150.2700016-1-chenjiahao16@huawei.com>
 <20230328115150.2700016-2-chenjiahao16@huawei.com>
 <ZCQewkvSpaI52DSM@MiWiFi-R3L-srv>
 <b8a32e3c-c083-20de-16d1-f628b02b739b@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <b8a32e3c-c083-20de-16d1-f628b02b739b@huawei.com>
Precedence: bulk

On 03/30/23 at 09:40pm, chenjiahao (C) wrote:
......
> Agreed, I will clean this up later in next version.
> > > +		if (ret || !crash_size)
> > > +			return;
> > > +
> > > +		/*
> > > +		 * crashkernel=Y,low is valid only when crashkernel=X,high
> > > +		 * is passed and high memory is reserved successful.
> > > +		 */
> > > +		ret = parse_crashkernel_low(boot_command_line, 0, &crash_low_size, &crash_base);
> > > +		if (ret == -ENOENT)
> > > +			crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE;
> > > +		else if (ret)
> > > +			return;
> > > +
> > > +		search_start = dma32_phys_limit;
> > > +	} else if (ret || !crash_size) {
> > > +		/* Invalid argument value specified */
> > >   		return;
> > > +	}
> > >   	crash_size = PAGE_ALIGN(crash_size);
> > > @@ -1201,16 +1246,26 @@ static void __init reserve_crashkernel(void)
> > >   	 */
> > >   	crash_base = memblock_phys_alloc_range(crash_size, PMD_SIZE,
> > >   					       search_start,
> > > -					       min(search_end, (unsigned long) SZ_4G));
> > > +					       min(search_end, (unsigned long)dma32_phys_limit));
> > >   	if (crash_base == 0) {
> > The above conditional check isn't right. If crashkernel=size@offset
> > specified, the reservation failure won't trigger retry. This seems to be
> > originally introduced by old commit, while this need be fixed firstly.
> 
> Just a little curious about the rule to cope with this specific case. If
> "crashkernel=size@offset" was passed
> 
> but reserve failed, should try again to allocate in high memory, regardless
> the specified size@offset,
> 
> or just throw a warning and return? Since I noticed the current logic here
> on Arm64 is to check if !fixed_base first

Yeah, we need mark the "crashkernel=size@offset" case and avoid to
retry. Because you won't succeed if  memblock has already failed to
reserve an unavailable memory region, retry is meaningless. This has
been done in x86, arm64.