1 .. SPDX-License-Identifier: GPL-2.0
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4 s390 (IBM Z) Protected Virtualization dumps
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6
7 Summary
8 -------
9
10 Dumping a VM is an essential tool for debuggin
11 it. This is especially true when a protected V
12 there's no way to access its memory and regist
13 while it's running.
14
15 However when dumping a protected VM we need to
16 confidentiality until the dump is in the hands
17 should be the only one capable of analysing it
18
19 The confidentiality of the VM dump is ensured
20 provides an interface to KVM over which encryp
21 can be requested. The encryption is based on t
22 Communication Key which is the key that's used
23 way that the customer is able to decrypt.
24
25
26 Dump process
27 ------------
28
29 A dump is done in 3 steps:
30
31 **Initiation**
32
33 This step initializes the dump process, genera
34 and extracts dump keys with which the VM dump
35
36 **Data gathering**
37
38 Currently there are two types of data that can
39 the memory and the vcpu state.
40
41 The vcpu state contains all the important regi
42 point, vector, control and tod/timers of a vcp
43 contain incomplete data if a vcpu is dumped wh
44 emulated with help of the hypervisor. This is
45 in the dump data. For the same reason it is ve
46 write out the encrypted vcpu state, but also t
47 from the hypervisor.
48
49 The memory state is further divided into the e
50 metadata comprised of the encryption tweaks an
51 encrypted memory can simply be read once it ha
52 time of the export does not matter as no re-en
53 needed. Memory that has been swapped out and h
54 read from the swap and written to the dump tar
55 special actions.
56
57 The tweaks / status flags for the exported pag
58 from the Ultravisor.
59
60 **Finalization**
61
62 The finalization step will provide the data ne
63 decrypt the vcpu and memory data and end the d
64 step completes successfully a new dump initiat
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