On 5/12/2021 12:19 PM, Stefan Hajnoczi wrote: > On Fri, May 07, 2021 at 05:25:05AM -0700, Steve Sistare wrote: >> To use the restart mode, qemu must be started with the memfd-alloc machine >> option. The memfd's are saved to the environment and kept open across exec, >> after which they are found from the environment and re-mmap'd. Hence guest >> ram is preserved in place, albeit with new virtual addresses in the qemu >> process. The caller resumes the guest by calling cprload, which loads >> state from the file. If the VM was running at cprsave time, then VM >> execution resumes. cprsave supports any type of guest image and block >> device, but the caller must not modify guest block devices between cprsave >> and cprload. > > Does QEMU's existing -object memory-backend-file on tmpfs or hugetlbfs > achieve the same thing?
Not quite. Various secondary anonymous memory objects are allocated via ram_block_add and must be preserved, such as these on x86_64. vga.vram pc.ram pc.bios pc.rom vga.rom rom@etc/acpi/tables rom@etc/table-loader rom@etc/acpi/rsdp Even the read-only areas must be preserved rather than recreated from files in the updated qemu, as their contents may have changed. - Steve
