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docs/migration Specify migration v3 and STATIC_DATA_END
Migration data can be split into two parts - that which is invariant of guest execution, and that which is not. Separate these two with the STATIC_DATA_END record. The short term, we want to move the x86 CPU Policy data into the stream. In the longer term, we want to provisionally send the static data only to the destination as a more robust compatibility check. In both cases, we will want a callback into the higher level toolstack. Mandate the presence of the STATIC_DATA_END record, and declare this v3, along with instructions for how to compatibly interpret a v2 stream. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
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@@ -127,7 +127,7 @@ marker 0xFFFFFFFFFFFFFFFF.
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id 0x58454E46 ("XENF" in ASCII).
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version 0x00000002. The version of this specification.
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version 0x00000003. The version of this specification.
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options bit 0: Endianness. 0 = little-endian, 1 = big-endian.
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@@ -620,6 +620,21 @@ The count of pfns is: record->length/sizeof(uint64_t).
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\clearpage
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STATIC_DATA_END
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---------------
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A static data end record marks the end of the static state. I.e. state which
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is invariant of guest execution.
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0 1 2 3 4 5 6 7 octet
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+-------------------------------------------------+
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The end record contains no fields; its body_length is 0.
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\clearpage
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Layout
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======
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@@ -639,7 +654,9 @@ A typical save record for an x86 PV guest image would look like:
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* Image header
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* Domain header
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* X86_PV_INFO record
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* Static data records:
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* X86_PV_INFO record
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* STATIC_DATA_END
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* X86_PV_P2M_FRAMES record
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* Many PAGE_DATA records
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* X86_TSC_INFO
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@@ -667,6 +684,8 @@ A typical save record for an x86 HVM guest image would look like:
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* Image header
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* Domain header
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* Static data records:
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* STATIC_DATA_END
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* Many PAGE_DATA records
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* X86_TSC_INFO
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* HVM_PARAMS
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@@ -675,9 +694,23 @@ A typical save record for an x86 HVM guest image would look like:
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HVM_PARAMS must precede HVM_CONTEXT, as certain parameters can affect
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the validity of architectural state in the context.
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Compatibility with older versions
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=================================
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v3 compat with v2
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-----------------
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A v3 stream is compatible with a v2 stream, but mandates the presense of a
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STATIC_DATA_END record ahead of any memory/register content. This is to ease
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the introduction of new static configuration records over time.
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A v3-compatible reciever interpreting a v2 stream should infer the position of
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STATIC_DATA_END based on finding the first X86_PV_P2M_FRAMES record (for PV
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guests), or PAGE_DATA record (for HVM guests) and behave as if STATIC_DATA_END
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had been sent.
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Legacy Images (x86 only)
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========================
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------------------------
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Restoring legacy images from older tools shall be handled by
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translating the legacy format image into this new format.
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@@ -36,6 +36,7 @@ static const char *const mandatory_rec_types[] =
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[REC_TYPE_VERIFY] = "Verify",
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[REC_TYPE_CHECKPOINT] = "Checkpoint",
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[REC_TYPE_CHECKPOINT_DIRTY_PFN_LIST] = "Checkpoint dirty pfn list",
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[REC_TYPE_STATIC_DATA_END] = "Static data end",
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};
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const char *rec_type_to_str(uint32_t type)
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@@ -73,6 +73,7 @@ struct xc_sr_rhdr
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#define REC_TYPE_VERIFY 0x0000000dU
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#define REC_TYPE_CHECKPOINT 0x0000000eU
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#define REC_TYPE_CHECKPOINT_DIRTY_PFN_LIST 0x0000000fU
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#define REC_TYPE_STATIC_DATA_END 0x00000010U
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#define REC_TYPE_OPTIONAL 0x80000000U
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@@ -56,6 +56,7 @@ REC_TYPE_x86_pv_vcpu_msrs = 0x0000000c
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REC_TYPE_verify = 0x0000000d
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REC_TYPE_checkpoint = 0x0000000e
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REC_TYPE_checkpoint_dirty_pfn_list = 0x0000000f
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REC_TYPE_static_data_end = 0x00000010
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rec_type_to_str = {
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REC_TYPE_end : "End",
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@@ -74,6 +75,7 @@ rec_type_to_str = {
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REC_TYPE_verify : "Verify",
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REC_TYPE_checkpoint : "Checkpoint",
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REC_TYPE_checkpoint_dirty_pfn_list : "Checkpoint dirty pfn list",
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REC_TYPE_static_data_end : "Static data end",
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}
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# page_data
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