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Suggested-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
54 lines
1.8 KiB
Plaintext
54 lines
1.8 KiB
Plaintext
=================
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VMCoreInfo device
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=================
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The `-device vmcoreinfo` will create a fw_cfg entry for a guest to
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store dump details.
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etc/vmcoreinfo
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**************
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A guest may use this fw_cfg entry to add information details to qemu
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dumps.
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The entry of 16 bytes has the following layout, in little-endian::
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#define VMCOREINFO_FORMAT_NONE 0x0
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#define VMCOREINFO_FORMAT_ELF 0x1
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struct FWCfgVMCoreInfo {
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uint16_t host_format; /* formats host supports */
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uint16_t guest_format; /* format guest supplies */
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uint32_t size; /* size of vmcoreinfo region */
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uint64_t paddr; /* physical address of vmcoreinfo region */
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};
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Only full write (of 16 bytes) are considered valid for further
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processing of entry values.
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A write of 0 in guest_format will disable further processing of
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vmcoreinfo entry values & content.
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You may write a guest_format that is not supported by the host, in
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which case the entry data can be ignored by qemu (but you may still
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access it through a debugger, via vmcoreinfo_realize::vmcoreinfo_state).
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Format & content
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****************
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As of qemu 2.11, only VMCOREINFO_FORMAT_ELF is supported.
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The entry gives location and size of an ELF note that is appended in
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qemu dumps.
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The note format/class must be of the target bitness and the size must
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be less than 1Mb.
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If the ELF note name is "VMCOREINFO", it is expected to be the Linux
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vmcoreinfo note (see Documentation/ABI/testing/sysfs-kernel-vmcoreinfo
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in Linux source). In this case, qemu dump code will read the content
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as a key=value text file, looking for "NUMBER(phys_base)" key
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value. The value is expected to be more accurate than architecture
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guess of the value. This is useful for KASLR-enabled guest with
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ancient tools not handling the VMCOREINFO note.
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