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Violators will be prosecuted for from ; Mon, 25 Jun 2018 09:29:51 +0100 References: <20180622194736.GA5794@roeck-us.net> <126ac556-0602-b927-58f5-cb5f65a5e0ec@de.ibm.com> <88d9afed-f91d-c320-13c8-9a93fc52b700@de.ibm.com> <20180625100548.64222dad.cohuck@redhat.com> From: Christian Borntraeger Date: Mon, 25 Jun 2018 10:29:46 +0200 MIME-Version: 1.0 In-Reply-To: <20180625100548.64222dad.cohuck@redhat.com> Content-Language: en-US Message-Id: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] s390 qemu boot failure in -next List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: Guenter Roeck , Martin Schwidefsky , Vasily Gorbik , Heiko Carstens , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-s390x , qemu-devel , Thomas Huth On 06/25/2018 10:05 AM, Cornelia Huck wrote: > On Mon, 25 Jun 2018 09:27:59 +0200 > Christian Borntraeger wrote: > >> Also adding QEMU. >> >> On 06/25/2018 09:10 AM, Christian Borntraeger wrote: >>> >>> >>> On 06/22/2018 09:47 PM, Guenter Roeck wrote: >>>> Hi, >>>> >>>> starting with commit 's390/boot: make head.S and als.c be part of the >>>> decompressor only' in -next, s390 immages no longer boot in qemu. >>>> As far as I can see, the reason is that the command line is no longer >>>> passed from qemu to the kernel, which results in a panic because the >>>> root file system can not be mounted. >>>> >>>> Was this change made on purpose ? If so, is there a way to get qemu >>>> back to working ? >>> >>> Certainly not on purpose. >>> >>> Vasily, I can reproduce this with KVM and an external kernel boot of the vmlinux file (the elf file) >>> >>> e.g. >>> >>> qemu-system-s390 -enable-kvm -nographic -kernel vmlinux -append "this string no longer is command line" >>> >>> The compressed image (bzImage) seems to work fine though. >>> >>> This seems to be an unfortunate side effect of QEMUs ways to "guess" its Linux (checking for start >>> address 0x10000, which is no longer true for the vmlinux file). With the pure vmlinux elf file >>> the load address is 0x100000 as there is no unpacker. > > Do we consider these locations to be an exported interface, or is it > just QEMU guessing? It is using what zipl has hardcoded. This works fine for the final image (with the unpacker), but being able to boot the elf file was just a very nice feature of QEMU. > >>> >>> Guenter, can you check if arch/s390/boot/bzImage works for you as a workaround? >> >> Something like this in QEMU >> >> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c >> index f278036fa7..14153ce880 100644 >> --- a/hw/s390x/ipl.c >> +++ b/hw/s390x/ipl.c >> @@ -187,11 +187,13 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp) >> */ >> if (pentry == KERN_IMAGE_START || pentry == 0x800) { >> ipl->start_addr = KERN_IMAGE_START; >> - /* Overwrite parameters in the kernel image, which are "rom" */ >> - strcpy(rom_ptr(KERN_PARM_AREA), ipl->cmdline); >> } else { >> ipl->start_addr = pentry; >> } >> + if (ipl->cmdline) { >> + /* If there is a command line, put it in the right place */ >> + strcpy(rom_ptr(KERN_PARM_AREA), ipl->cmdline); >> + } > > Check for the magic Linux string (like in the non-elf case) first? Even that does not exists in vmlinux but only in bzImage with the latest patchset (in next, but not upstream yet) > >> >> if (ipl->initrd) { >> ram_addr_t initrd_offset; >> >> would put the command line in no matter what the start address is. > > I'm for putting that one in (and backporting it to qemu-stable). It's a > bit worrying, though, that our ipl code is so fragile... We actually have to combine this with Thomas fix (to check for rom_ptr returning something sane). It seems that ipl->commandline is always there, so we have to check for strlen!=0 it seems.. I mean if somebody ask for "-append something" we can certainly always write something if there is rom/ram.