linux-kernel - Re: [PATCH v2 4/7] s390/physmem_info: query diag500(STORAGE LIMIT) to support QEMU/KVM memory devices

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Message-ID: <0224bd06-3a77-474e-917d-814d2082186e@redhat.com>
Date: Thu, 17 Oct 2024 16:36:51 +0200
From: David Hildenbrand <david@...hat.com>
To: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 linux-s390@...r.kernel.org, virtualization@...ts.linux.dev,
 linux-doc@...r.kernel.org, kvm@...r.kernel.org,
 Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>, Thomas Huth <thuth@...hat.com>,
 Cornelia Huck <cohuck@...hat.com>, Janosch Frank <frankja@...ux.ibm.com>,
 Claudio Imbrenda <imbrenda@...ux.ibm.com>,
 "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
 <eperezma@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>,
 Jonathan Corbet <corbet@....net>, Mario Casquero <mcasquer@...hat.com>
Subject: Re: [PATCH v2 4/7] s390/physmem_info: query diag500(STORAGE LIMIT) to
 support QEMU/KVM memory devices

On 17.10.24 16:32, Alexander Gordeev wrote:
> On Thu, Oct 17, 2024 at 02:07:12PM +0200, David Hildenbrand wrote:
>> On 17.10.24 12:00, David Hildenbrand wrote:
>>> Well, DIAGNOSE 260 is z/VM only and DIAG 500 is KVM only. So there are
>>> currently not really any other reasonable ways besides SCLP.
>>
>> Correction: Staring at the code again, in detect_physmem_online_ranges()
>> we will indeed try:
>>
>> a) sclp_early_read_storage_info()
>> b) diag260()
> 
> So why care to call diag260() in case of DIAGNOSE 500? What about the below?
> 
> void detect_physmem_online_ranges(unsigned long max_physmem_end)
> {
> 	if (!sclp_early_read_storage_info()) {
> 		physmem_info.info_source = MEM_DETECT_SCLP_STOR_INFO;
> 	} else if (physmem_info.info_source == MEM_DETECT_DIAG500_STOR_LIMIT) {
> 		unsigned long online_end;
> 
> 		if (!sclp_early_get_memsize(&online_end)) {
> 			physmem_info.info_source = MEM_DETECT_SCLP_READ_INFO;
> 			add_physmem_online_range(0, online_end);
> 		}
> 	} else if (!diag260()) {
> 		physmem_info.info_source = MEM_DETECT_DIAG260;
> 	} else if (max_physmem_end) {
> 		add_physmem_online_range(0, max_physmem_end);
> 	}
> }

Works for me, thanks!

-- 
Cheers,

David / dhildenb