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dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:57940 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kfzWU-0007iE-K6 for qemu-devel@archiver.kernel.org; Fri, 20 Nov 2020 01:03:54 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:46006) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kfzVU-0007EI-QH for qemu-devel@nongnu.org; Fri, 20 Nov 2020 01:02:52 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:41993) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kfzVR-0002TJ-55 for qemu-devel@nongnu.org; Fri, 20 Nov 2020 01:02:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605852167; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=i0km6savy83xWYHMPW9gVVE4CpNf2YosuwV6lq5llAM=; b=HXvhzh37+uZG1P49lcpRaj8j3EkovWoxxrZ8NvQChLwFeGCoiTQRf911fbfZQh6qFcj06w A39UZYuXnJb9BCqG+giT8NR68iJFLfTOufBllUspRt3m0TMUIDIny8ALrGi/LMvnfdJHTC 5hRBTEuAE2v0lR2rFOMTMAkVl+b73lg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-335--WdJjroANZm6D4G5iaeqtw-1; Fri, 20 Nov 2020 01:02:43 -0500 X-MC-Unique: -WdJjroANZm6D4G5iaeqtw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EB68918B6126; Fri, 20 Nov 2020 06:02:41 +0000 (UTC) Received: from thuth.remote.csb (ovpn-112-135.ams2.redhat.com [10.36.112.135]) by smtp.corp.redhat.com (Postfix) with ESMTP id A82FC5D9D0; Fri, 20 Nov 2020 06:02:39 +0000 (UTC) Subject: Re: [PATCH 2/2] pc-bios: s390x: Give precedence to reset PSW To: Eric Farman , Cornelia Huck References: <20201119165729.63351-1-farman@linux.ibm.com> <20201119165729.63351-3-farman@linux.ibm.com> <8595991c-5776-3021-ca16-deebba287be1@redhat.com> <7f99cc7c-f74d-0721-3749-515208526bb0@linux.ibm.com> From: Thomas Huth Message-ID: Date: Fri, 20 Nov 2020 07:02:38 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <7f99cc7c-f74d-0721-3749-515208526bb0@linux.ibm.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jason Herne , Janosch Frank , Matthew Rosato , qemu-devel@nongnu.org, Christian Borntraeger , qemu-s390x@nongnu.org, Jared Rossi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 19/11/2020 22.11, Eric Farman wrote: > > > On 11/19/20 3:20 PM, Thomas Huth wrote: >> On 19/11/2020 17.57, Eric Farman wrote: >>> Let's look at the Reset PSW first instead of the contents of memory. >>> It might be leftover from an earlier system boot when processing >>> a chreipl. >>> >>> Signed-off-by: Eric Farman >>> --- >>>   pc-bios/s390-ccw/jump2ipl.c | 20 ++++++++++---------- >>>   1 file changed, 10 insertions(+), 10 deletions(-) >>> >>> diff --git a/pc-bios/s390-ccw/jump2ipl.c b/pc-bios/s390-ccw/jump2ipl.c >>> index fbae45b03c..67b4afb6a0 100644 >>> --- a/pc-bios/s390-ccw/jump2ipl.c >>> +++ b/pc-bios/s390-ccw/jump2ipl.c >>> @@ -72,16 +72,6 @@ void jump_to_IPL_code(uint64_t address) >>>     void jump_to_low_kernel(void) >>>   { >>> -    /* >>> -     * If it looks like a Linux binary, i.e. there is the "S390EP" magic >>> from >>> -     * arch/s390/kernel/head.S here, then let's jump to the well-known >>> Linux >>> -     * kernel start address (when jumping to the PSW-at-zero address >>> instead, >>> -     * the kernel startup code fails when we booted from a network device). >>> -     */ >>> -    if (!memcmp((char *)0x10008, "S390EP", 6)) { >>> -        jump_to_IPL_code(KERN_IMAGE_START); >>> -    } >>> - >>>       /* Trying to get PSW at zero address */ >>>       if (*((uint64_t *)0) & RESET_PSW_MASK) { >>>           /* >>> @@ -92,6 +82,16 @@ void jump_to_low_kernel(void) >>>           jump_to_IPL_code(0); >>>       } >>>   +    /* >>> +     * If it looks like a Linux binary, i.e. there is the "S390EP" magic >>> from >>> +     * arch/s390/kernel/head.S here, then let's jump to the well-known >>> Linux >>> +     * kernel start address (when jumping to the PSW-at-zero address >>> instead, >>> +     * the kernel startup code fails when we booted from a network device). >>> +     */ >>> +    if (!memcmp((char *)0x10008, "S390EP", 6)) { >>> +        jump_to_IPL_code(KERN_IMAGE_START); >>> +    } >> >> That feels a little bit dangerous ... I assume the order has been that way >> for a reason, e.g. I think we had to jump to KERN_IMAGE_START for some older >> versions of the Linux kernel since the startup code that was referenced by >> the PSW at address zero was not working in KVM... > > Makes sense.  It does seem like a precarious piece of code. > >> >> What do you think about this alternate idea instead: Clear the memory at >> location 0x10008 at the very beginning of the main() function (or maybe in >> boot_setup())? > > This seems to work too (I put it in boot_setup(), prior to call to > store_iplb()). Great, can you send the patch before your holidays next week? (If you don't have enough time, that's ok, too, it's trivial enough, so I think I could write such a patch, too) Thomas