From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chao Fan Subject: Re: [PATCH v9 5/8] x86/boot: Add get_acpi_rsdp() to parse RSDP in cmdlien from kexec Date: Mon, 22 Oct 2018 15:30:51 +0800 Message-ID: <20181022073050.GB7641@localhost.localdomain> References: <20181017102012.872-1-fanc.fnst@cn.fujitsu.com> <20181017102012.872-6-fanc.fnst@cn.fujitsu.com> <20181021022650.GI1885@192.168.1.4> <20181022060613.GK1885@192.168.1.4> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <20181022060613.GK1885@192.168.1.4> Sender: linux-kernel-owner@vger.kernel.org To: Baoquan He Cc: dyoung@redhat.com, "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "linux-efi@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "bp@alien8.de" , "tglx@linutronix.de" , "mingo@redhat.com" , "hpa@zytor.com" , "keescook@chromium.org" , "msys.mizuma@gmail.com" , "Indoh, Takao" , "Cao, Jin" List-Id: linux-efi@vger.kernel.org On Mon, Oct 22, 2018 at 02:06:13PM +0800, Baoquan He wrote: >On 10/22/18 at 05:30am, Fan, Chao wrote: >> >> +static void get_acpi_rsdp(acpi_physical_address *rsdp_addr) >> >> +{ >> >> +#ifdef CONFIG_KEXEC >> >> + unsigned long long res; >> >> + int len = 0; >> >> + char *val; >> >> + >> >> + val = malloc(20); >> > >> >Why is the length 20? Defined a macro? >> > >> >> Not a calculation, if it's enough to store the address, that will be OK. > >Sorry, I didn't catch. It's 16 in setup_acpi_rsdp() of >drivers/acpi/osl.c . What does 'that' mean? The second parameter of kstrtoull(), the 16 you mentioned means hexadecimal, not the length. I checked my host and guest, the value are ACPI20=0xbfbfa014, ACPI20=0xdb807000. The length of memory is 8. Well the max memory address is 16, add "0x" and '\0' is 19. So I set it as 20. I am not sure whether 8 is enough for the address, if OK, 11 will be enough, or 19 is OK. If my understanding is wrong, please tell me. Thanks, Chao Fan > >Wondering why not making it 200, it's also enough to store the address. > >