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A guest OS that supports memory hotplug / memory devices must during boot be aware of the maximum possible physical memory address that it might have to handle at a later stage during its runtime. For example, the maximum possible memory address might be required to prepare the kernel virtual address space accordingly (e.g., select page table hierarchy depth). On s390x there is currently no such mechanism that is compatible with paravirtualized memory devices, because the whole SCLP interface was designed around the idea of "storage increments" and "standby memory". Paravirtualized memory devices we want to support, such as virtio-mem, have no intersection with any of that, but could co-exist with them in the future if ever needed. In particular, a guest OS must never detect and use device memory without the help of a proper device driver. Device memory must not be exposed in any firmware-provided memory map (SCLP or diag260 on s390x). For this reason, these memory devices will be places in memory *above* the "maximum storage increment" exposed via SCLP. Let's provide a new diag500 subcode to query the memory limit determined in s390_memory_init(). Message-ID: <20241219144115.2820241-8-david@redhat.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Thomas Huth <thuth@redhat.com> Signed-off-by: David Hildenbrand <david@redhat.com>
25 lines
772 B
C
25 lines
772 B
C
/*
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* Support for QEMU/KVM hypercalls on s390x
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*
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* Copyright IBM Corp. 2012, 2017
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* Author(s): Cornelia Huck <cornelia.huck@de.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or (at
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* your option) any later version. See the COPYING file in the top-level
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* directory.
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*/
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#ifndef HW_S390_HYPERCALL_H
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#define HW_S390_HYPERCALL_H
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#include "cpu.h"
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#define DIAG500_VIRTIO_NOTIFY 0 /* legacy, implemented as a NOP */
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#define DIAG500_VIRTIO_RESET 1 /* legacy */
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#define DIAG500_VIRTIO_SET_STATUS 2 /* legacy */
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#define DIAG500_VIRTIO_CCW_NOTIFY 3 /* KVM_S390_VIRTIO_CCW_NOTIFY */
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#define DIAG500_STORAGE_LIMIT 4
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void handle_diag_500(S390CPU *cpu, uintptr_t ra);
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#endif /* HW_S390_HYPERCALL_H */
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