From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fkmWO-0002n3-27 for kexec@lists.infradead.org; Wed, 01 Aug 2018 08:30:17 +0000 Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w718ThNS012489 for ; Wed, 1 Aug 2018 04:30:03 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2kk8s3sgxb-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 01 Aug 2018 04:30:03 -0400 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 1 Aug 2018 09:30:00 +0100 Date: Wed, 1 Aug 2018 10:29:51 +0200 From: Philipp Rudo Subject: Re: [PATCH v13 03/16] s390, kexec_file: drop arch_kexec_mem_walk() In-Reply-To: <20180801075820.3753-4-takahiro.akashi@linaro.org> References: <20180801075820.3753-1-takahiro.akashi@linaro.org> <20180801075820.3753-4-takahiro.akashi@linaro.org> MIME-Version: 1.0 Message-Id: <20180801102951.527cfc57@ThinkPad> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: AKASHI Takahiro Cc: herbert@gondor.apana.org.au, bhe@redhat.com, ard.biesheuvel@linaro.org, catalin.marinas@arm.com, bhsharma@redhat.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, heiko.carstens@de.ibm.com, dhowells@redhat.com, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, kexec@lists.infradead.org, schwidefsky@de.ibm.com, james.morse@arm.com, dyoung@redhat.com, davem@davemloft.net, vgoyal@redhat.com Hey Akashi, I kept thinking about this patch and remembered why I didn't made the change you are suggesting now. The problem is when you only check for kbuf->mem you are excluding address 0, which might be a valid address to load the kernel to. On s390 this is actually done when the kernel is not loaded via a boot loader. For kexec_file however, we cut off the first few kB of the image and jump directly to 'startup'. So checking for !0 does not cause a problem here. Anyway, the long term safer solution would be something like #define KEXEC_BUF_MEM_UNKNOWN (-1UL) for architectures to tell common code to search a fitting mem hole. Back then I didn't do the change because I had the other workaround, which didn't require a common code change. But when you are touching the code now it is worth thinking about it. Just wanted to let you know Philipp On Wed, 1 Aug 2018 16:58:07 +0900 AKASHI Takahiro wrote: > Since s390 already knows where to locate buffers, calling > arch_kexec_mem_walk() has no sense. So we can just drop it as kbuf->mem > indicates this while all other architectures sets it to 0 initially. > > This change is a preparatory work for the next patch, where all the > variant memory walks, either on system resource or memblock, will be > put in one common place so that it will satisfy all the architectures' > need. > > Signed-off-by: AKASHI Takahiro > Reviewed-by: Philipp Rudo > Cc: Martin Schwidefsky > Cc: Heiko Carstens > Cc: Dave Young > Cc: Vivek Goyal > Cc: Baoquan He > --- > arch/s390/kernel/machine_kexec_file.c | 10 ---------- > kernel/kexec_file.c | 4 ++++ > 2 files changed, 4 insertions(+), 10 deletions(-) > > diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c > index f413f57f8d20..32023b4f9dc0 100644 > --- a/arch/s390/kernel/machine_kexec_file.c > +++ b/arch/s390/kernel/machine_kexec_file.c > @@ -134,16 +134,6 @@ int kexec_file_add_initrd(struct kimage *image, struct s390_load_data *data, > return ret; > } > > -/* > - * The kernel is loaded to a fixed location. Turn off kexec_locate_mem_hole > - * and provide kbuf->mem by hand. > - */ > -int arch_kexec_walk_mem(struct kexec_buf *kbuf, > - int (*func)(struct resource *, void *)) > -{ > - return 1; > -} > - > int arch_kexec_apply_relocations_add(struct purgatory_info *pi, > Elf_Shdr *section, > const Elf_Shdr *relsec, > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index 63c7ce1c0c3e..bf39df5e5bb9 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -534,6 +534,10 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf) > { > int ret; > > + /* Arch knows where to place */ > + if (kbuf->mem) > + return 0; > + > ret = arch_kexec_walk_mem(kbuf, locate_mem_hole_callback); > > return ret == 1 ? 0 : -EADDRNOTAVAIL; _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec