vmcoreinfo.txt (1798B)
1 ================= 2 VMCoreInfo device 3 ================= 4 5 The `-device vmcoreinfo` will create a fw_cfg entry for a guest to 6 store dump details. 7 8 etc/vmcoreinfo 9 ************** 10 11 A guest may use this fw_cfg entry to add information details to qemu 12 dumps. 13 14 The entry of 16 bytes has the following layout, in little-endian:: 15 16 #define VMCOREINFO_FORMAT_NONE 0x0 17 #define VMCOREINFO_FORMAT_ELF 0x1 18 19 struct FWCfgVMCoreInfo { 20 uint16_t host_format; /* formats host supports */ 21 uint16_t guest_format; /* format guest supplies */ 22 uint32_t size; /* size of vmcoreinfo region */ 23 uint64_t paddr; /* physical address of vmcoreinfo region */ 24 }; 25 26 Only full write (of 16 bytes) are considered valid for further 27 processing of entry values. 28 29 A write of 0 in guest_format will disable further processing of 30 vmcoreinfo entry values & content. 31 32 You may write a guest_format that is not supported by the host, in 33 which case the entry data can be ignored by qemu (but you may still 34 access it through a debugger, via vmcoreinfo_realize::vmcoreinfo_state). 35 36 Format & content 37 **************** 38 39 As of qemu 2.11, only VMCOREINFO_FORMAT_ELF is supported. 40 41 The entry gives location and size of an ELF note that is appended in 42 qemu dumps. 43 44 The note format/class must be of the target bitness and the size must 45 be less than 1Mb. 46 47 If the ELF note name is "VMCOREINFO", it is expected to be the Linux 48 vmcoreinfo note (see Documentation/ABI/testing/sysfs-kernel-vmcoreinfo 49 in Linux source). In this case, qemu dump code will read the content 50 as a key=value text file, looking for "NUMBER(phys_base)" key 51 value. The value is expected to be more accurate than architecture 52 guess of the value. This is useful for KASLR-enabled guest with 53 ancient tools not handling the VMCOREINFO note.