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Wed, 30 Oct 2024 14:30:20 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 752C120043; Wed, 30 Oct 2024 14:30:20 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1C2E02004B; Wed, 30 Oct 2024 14:30:20 +0000 (GMT) Received: from li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com (unknown [9.155.204.135]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Wed, 30 Oct 2024 14:30:20 +0000 (GMT) Date: Wed, 30 Oct 2024 15:30:18 +0100 From: Alexander Gordeev To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, linux-doc@vger.kernel.org, kvm@vger.kernel.org, Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Morton , Jonathan Corbet , Mario Casquero Subject: Re: [PATCH v2 4/7] s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory devices Message-ID: References: <20241014144622.876731-1-david@redhat.com> <20241014144622.876731-5-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241014144622.876731-5-david@redhat.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: jcbMrInueqgSbuMhblYjsLoimVoh1fDK X-Proofpoint-ORIG-GUID: zWiWWhTbdgzaKB2WcP0riaikdeezGz5v X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=742 clxscore=1011 adultscore=0 mlxscore=0 priorityscore=1501 spamscore=0 malwarescore=0 impostorscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410300111 X-Stat-Signature: o5iu3zqqo51a9d3kk5j54padp7pqyw8i X-Rspamd-Queue-Id: 94FCD140024 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1730298611-405963 X-HE-Meta: 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 s6NIayPh appewr3nhfWyhr3TdoLyciWuF31vQUbJs+V6hBlyhMbl5OWIvEDoaznps3y1uujNgkYMkyQDNJqk1Vg8rCBcuqwHv9YJJpVYPDwB9bbTdJNUsfHAwXUX8QRuNYz2CsBPtO8oCkpGRkMKCRfi2HkUIzK67zjqNIAVJ8fgYtbghhnQQLWRlhwOi878Gznz836T9QoUhJSV4J+m5cKmT34BZAeE2KD0J6aK1psI6bdwDN+NOw7ucTSPDc72wnics8WRgqBoXQPUu/orAGEpzj1XRsp6S5p5ZRcvCtkfvba1w+3zVG7vp2A/UgH8N5jhUvypD9x51ULojw7JQugk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Oct 14, 2024 at 04:46:16PM +0200, David Hildenbrand wrote: Hi David, > To support memory devices under QEMU/KVM, such as virtio-mem, > we have to prepare our kernel virtual address space accordingly and > have to know the highest possible physical memory address we might see > later: the storage limit. The good old SCLP interface is not suitable for > this use case. > > In particular, memory owned by memory devices has no relationship to > storage increments, it is always detected using the device driver, and > unaware OSes (no driver) must never try making use of that memory. > Consequently this memory is located outside of the "maximum storage > increment"-indicated memory range. > > Let's use our new diag500 STORAGE_LIMIT subcode to query this storage > limit that can exceed the "maximum storage increment", and use the > existing interfaces (i.e., SCLP) to obtain information about the initial > memory that is not owned+managed by memory devices. > > If a hypervisor does not support such memory devices, the address exposed > through diag500 STORAGE_LIMIT will correspond to the maximum storage > increment exposed through SCLP. > > To teach kdump on s390 to include memory owned by memory devices, there > will be ways to query the relevant memory ranges from the device via a > driver running in special kdump mode (like virtio-mem already implements > to filter /proc/vmcore access so we don't end up reading from unplugged > device blocks). > > Tested-by: Mario Casquero > Signed-off-by: David Hildenbrand > --- > arch/s390/boot/physmem_info.c | 46 ++++++++++++++++++++++++++-- > arch/s390/include/asm/physmem_info.h | 3 ++ > 2 files changed, 46 insertions(+), 3 deletions(-) Reviewed-by: Alexander Gordeev Thanks!